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109. Explain the development of a secondary oocyte 116. Explain the ovarian and uterine events that occur (ovum) in a human female from the embryonic during a menstrual cycle in a human female, stage upto its ovulation. Name the hormones under the influence of pituitary and ovarian involved in this process.  [Delhi 2015] hormones respectively. [Delhi 2014] OR 117. The following is the illustration of the sequence When and where are primary oocytes formed of ovarian events “A” to “I” in a human female. in a human female? Trace the development of oocytes till ovulation in menstrual cycle. How do gonadotropins influence this developmental A B C D E F G H I process?[Delhi 2010] (a) Identify the figure that illustrates ovulation 110. (a) N a m e t h e h o r m o n e t h a t i n i t i a t e s and mention the stage of oogenesis it spermatogenesis in humans. Describe the represents. process of spermatogenesis in sequence (b) Name the ovarian hormone and the pituitary mentioning the ploidy of the cells at each step hormone that have caused the above entry into the ovum.  mentioned event. (b) Draw the diagram of a mature human sperm (c) Explain the changes that occur in the uterus and label the parts that. simultaneously in anticipation. (i) helps in reaching to the ovum. (ii) providing energy for it to reach the ovum. (d) Write the difference between ‘C’ and ‘H’. (iii) helping it to gain entry into the ovum. (e) Draw a labelled sketch of the structure of a [Delhi 2015 C] human ovum prior to fertilisation. 111. Describe the events of spermatogenesis with [Delhi 2012] the help of a schematic repre-sentation. Write 118. Draw a labelled diagram of human female two differences between spermatogenesis and reproductive system. Enumerate the events in oogenesis.  [Delhi 2013] the ovary of a human female during (i) Follicular 112. Give schematic representation of oogenesis phase (ii) Luteal phase of menstrual cycle. in humans. Mention the number of chromosomes [Delhi 2011] at each stage. Correlate the life phases of the 119. Briefly explain the events of fertilization individual with the stages of process. and implantation in an adult human female. [Delhi 2008] Comment on the role of placenta as an endocrine 113. (a) Where does spermatogenesis occur in gland.  [Delhi 2016 ] human testes? Describe the process of 120. Mention the site of fertilization of a human ovum. spermatogenesis upto the formation of List the events that follow in sequence until the spermatozoa. implantation of the blastocyst.  [Delhi 2015 C] (b) Trace the path of spermatozoa from the testes 121. Explain the events taking place at the time of upto the ejaculatory duct only. fertilization of an ovum in a human female. [Foreign 2016] Trace the development of the zygote upto its 114. Study the following flow chart. Name the implantation in the uterus. Name and draw a hormones involved at each stage. labelled sectional view of the embryonic stage Ovulation that gets implanted. [Delhi 2010] ↓ OR Pregnancy Explain the process of fertilization and lactation implantation in humans. [Foreign 2015] ↓ 122. (a) Draw a transverse section of human Placenta ovary showing the sequential development ↓ of different follicles up to the corpus luteum. Foetal growth (b) Comment on the corresponding ovarian and ↓ pituitary hormone levels during these events. Parturition [Foreign 2009] [All India 2014 C] 115. Describe the changes that occur in ovaries and uterus in human female during the reproductive 123. (a) Describe the events of oogenesis with the help cycle.[Delhi 2015] of schematic representation. 50 Biology–12

OR (b) Identify the ovarian phases during a menstrual cycle E x p l a i n w i t h t h e h e l p o f s c h e m a t i c (i) 5th day to 12th day of the cycle representation the process of formation of (ii) 14th day of the cycle (iii) 16th day to 25th day of the cycle. mature gamete in a human female. (c) Explain the ovarian events (i), (ii) and (iii) (b) How is spermatogenesis different from the under the influence of hormones ‘X’ and ‘Y’. process mentioned above? Explain. [All India 2008 C] 132. (a) Explain the process of fertilisation of an [All India 2011 C] ovum in humans. Trace the events that occur OR after fertilisation upto the implantation of blastocyst. Write two differences between oogenesis and (b) Draw a labelled diagram of a human blastocyst. spermatogenesis.[Delhi 2013 C] [Delhi 2010, All India 2010 C, 2012 C] 124. Draw a labelled diagram of the microscopic 133. (a) Mention the event that induces the completion structure of a human sperm. Explain the of the meiotic division of the secondary oocyte. functions of each part. [Delhi 2012 C] (b) Trace the journey of the ovum from the ovary, its fertilisation and further development until 125. (a) Describe the stages of oogenesis in human the implantation of the embryo. females. [All India 2010 C] (b) Draw a labelled diagram of a human ovum 134. released after ovulation. [Delhi 2011] 126. (a) Describe with the help of schematic diagram the process of spermatogenesis in a human male. (b) Draw a labelled diagram of mature sperm. [All India 2011 C, 2010] 127. (a) Draw a schematic diagram of a human sperm and label the cellular components (b) Give the functions of any three parts. [Delhi 2009] 128. Explain the different stages of oogenesis in humans starting from foetal life till its completion. When and where in body is oogenesis completed? [Delhi 2009 C] 129. (a) G i v e a s c h e m a t i c r e p r e s e n t a t i o n o f spermatogenesis in humans. (a) One of the sperms is observed to penetrate ‘A’ (b) At which stage of life does gametogenesis of the ovum, as shown in the above diagram. begin in human male and female respectively? Name ‘A’. (c) Name the organs where gametogenesis (b) How is the sperm able to do so? gets completed in human male and female (c) Where exactly in the Fallopian tube does this respectively.[Delhi 2008] occur? 130. Draw a labelled sectional view of a human ovary. Explain the events of oogenesis.  [Delhi 2008 C] (d) Explain the events thereafter upto morula 131. Study the graph given below and answer the stage.[All India 2013 C] questions that follow: 135. (a) Explain the following phases in the menstrual cycle of a human female: Pituitary Hormone levels (i) Menstrual phase (ii) Follicular phase (iii) Luteal phase (b) A proper understanding of menstrual cycle XY can help immensely in family planning. Do you agree with the statement ? Provide reasons for your answer. [All India 2017] 136. (a) Explain menstrual cycle in human females. 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29/1 (b) How can the scientific understanding of the Days menstrual cycle of human females help as a (a) Name the hormones ‘X’ and ‘Y’. contraceptive measure? [CBSE 2018] Human Reproduction  51

Answers I. Multiple Choice Questions 9. Acrosome is present on the anterior portion of the head of sperm. It contains enzymes which help 1. (c) 2. (d) 3. (d) 4. (b) 5. (a) sperm to gain entry in ovum. 6. (b) 7. (a) 8. (b) 9. (c) 10. (c) 11. (d) 12. (b) 13. (c) 14. (b) 15. (a) 10. Meiotic division gets completed in tertiary follicle and the secondary oocyte is formed, the tertiary II. Fill in the Blanks follicle gets mature to become graaffin follicle. 1. menarche 2. oogenesis 11. Sertoli cells and are present in semini-ferous 3. progesterones 4. Graafian follicle tubules. 5. parturition 6. colostrum 7. implantation 8. fertilisation. 12. Refer answer no. 11. 13. Refer answer no. 1. III. True or False 14. Refer answer no. 1 15. Refer answer no. 2 (ii) 1. False 2. True 3. False 4. True 5. False 16. They collect the egg released from ovary 6. True 7. True 8. True 9. False 10. False 17. Oogenesis is initiated in foetal stage and IV. Match the items of Column I with those of spermatogenesis is initiated once the child Column II: reaches puberty. 1. (b) 2. (b) 18. Refer answer no. 9. 19. Refer answer no. 17. 1 Mark Questions 20. Refer answer no. 3. It occurs in seminiferous 1. Testes are located outside the abdominal cavity to tubule. maintain 2–2.5°C temperature lower than body, this is necessary for efficient spermatogenesis. 21. Sperm has to move in female reproductive tract, The pouch in which they are present is called in order to fertilize egg in fallopian tubules. scrotum. 22. Secretory/luteal phase. Corpus luteum secretes 2. (i) Sertoli cells: Location–seminiferous tubule; progesterone to stimulate uterine gland. Function–provide nutrition to the developing sperms. 23. At this age menopause occurs and no more eggs are released. (ii) Leydig cells: Location–interstitial space present between seminiferous tubules within 24. Refer answer no. 6. testes; Function-secrete male androgen, 25. Sperm comes in contact with zona pellucida, it testosterone. induces changes in the membrane. The enzymes 3. Spermiogenesis Spermiation from acrosome are released as the nucleus of sperm enters ovum. Process of development Process of release of 26. Structure is blastula 'A' – is trophoblast. of spermatozoa from spermatozoa from 2 Marks Questions spermatids. seminiferous tubules. 27. Oxytocin acts on uterine muscle, causes stronger 4. (i) If ovum is fertilized, corpus luteum secretes uterine contraction which leads to expulsion of progesterone which helps in maintaining the foetus out of uterus. uterus lining which holds the foetus. Foetal ejection reflex triggers its release from the (ii) If ovum is not fertilized, the corpus luteum pituitary. degenerates, the sudden fall in level of progesterone causes breaking of uterus lining 28. Fertilisation occurs at the ampullary isthmus and hence bleeding. This begins new cycle of junction of fallopian tube when sperm and egg menstruation. reach this region simultaneously. Acrosome of the sperm releases enzymes which allow the sperm 5. Colostrum contains several antibodies which to enter the egg. Entry of sperm stimulates provides initial protection to the infant against secondary oocyte to complete its second meiotic diseases. division. This produces egg and second polar body. Nucleus of sperm and ovum fuses to form 6. During fertilisation, a sperm comes in contact diploid zygote. with the zona pellucida layer of the ovum which induces changes in the membrane that blocks the 29. Fimbriae are finger like projections present at entry of additional sperms. the mouth of fallopian tube called infundibulum. They collect ovum after ovulation and passes it 7. The trophoblast layer of blastocyst gets attached to fallopian tube. to the endometrium of the uterus. 8. Blastula. 52 Biology–12

30. Plasma membrane 38. Menarche is the start of menstrual cycle at the Acrosome age of 12-13. Head Nucleus containing Menopause marks the end of menstrual cycle in chromosomal material human female which occurs at the age of 45-55. Head of a Human Sperm 39. Gonadotropins such as LH and FSH increase gradually during follicular phase and secretory 31. At puberty there is significant increase in the phase respectively. FSH stimulates the secretion of gonadotropin releasing hormone from development of follicles, LH causes ovulation hypothalamus. This hormone acts on the anterior that stimulates the formation of corpus pituitary gland and stimulates the secretion of luteum which in turn secretes progesterone. two gonadotropins - Luteinising hormone (LH) These gonadotropins reach peak at the middle and follicle stimulating hormone (FSH). LH acts of cycle, i.e. about 14th day of menstrual cycle. on the Leydig cells and stimulates synthesis and secretion of androgens. Androgens, in turn, 40. Sertoli cells provide nutrition to germ cells during stimulate the process of spermatogenesis. FSH spermatogenesis. acts on the sertoli cells and stimulates secretion of some factors which help in the process of 41. Refer answer no. 1. spermiogenesis. 42. Uterine cavity Uterine fundus 32. Leydig cells are present between semini-ferous tubules, within testes. They secrete male Isthmus androgen, testosterone. Testosterone stimulates Ampulla Fallopian the process of spermatogenesis and is also Infundibulum tube required to maintain the function of male sex accessory ducts and glands. Endometrium Ovary Myometrium Fimbriae 33. Myometrium: Is the middle layer of uterus. It contracts the uterus during child birth Perimetrium Cervix Cervical canal Endometrium: It is the inner glandular layer of uterus, it undergoes cyclic changes Vagina during menstruation and implantation of embryo takes place. Diagrammatic sectional view of the female reproductive system 34. Refer answer no. 25. 35. Finger like projections called chorionic villi 43. Refer answer no. 33. 44. External–Membranous perimetrium. develop from trophoblast layer of blastula after Middle–muscular myometrium it gets embedded in the uterine wall. Internal–Glandular endometrium. 45. Testes: Produces sperms and testos-terone. Function: Ovary: Produces egg and oestrogen. (i) It forms placenta, which acts as a link 46. Refer answer no. 31. between mother and foetus 47. Plasma membrane (ii) It supplies oxygen and nutrients from mother Head Acrosome to foetus and removes CO2. Nucleus containing chromosomal material (iii) It excretes waste from foetus into maternal blood Neck 36. High concentration of LH acts on graafian follicle Middle Piece and causes it to rupture to release ovum. Mitochondria (energy source for swimming) 37. During follicular phase: LH and FSH gradually increase, estrogen is produced by the ovary, Tail uterine wall is repaired, development of follicle occurs from primary follicle to graafian follicle. Structure of sperm During luteul phase: LH and FSH decreases, corpus luteum secretes progesterone and uterine 48. 2nd meiotic division. Completes when sperm wall grows to get ready for implantation. nucleus enters ovum. 49. Refer answer no. 47 50. (a) Provides energy for movement of tail (b) LH hormone act on leydig cells and stimulate the synthesis and secretion of androgen testosterone. Human Reproduction  53

51. A–Leydig cell The blastocyst completely gets embedded in B–Stimulates follicular development uterus. C–Spermatogenesis D–Ovulation 63. Blastula. 52. (a) spermatogonium (a) A–inner cell mass B –Trophoblast. (b) Primary spermatocytes (b) Inner cell mass forms foetus (c) Spermatid 64. Morula is formed in fallopian tube. Zygote divides (d) Secondary spermatocyte to form morula by repeated mitotic divisions upto 8-16 celled stage. (e) Spermatozoa 65. (a) Signals of parturition originates from fully (f) Sertoli cells developed foetus. 53. Granulosa cells (b) Colostrum contains several antibodies which Basal lamina provide immunity to newborns. Antrum Corona radiata 66. Parturition is called neuroendocrine mechanism because both neural signals and hormonal Structure of the Graafian follicle secretions lead to parturition. 54. Males Females 67. Colostrum is the first milk secreted from the mammary glands of mother after child birth. It contains. many antibodies which provide immunity to new borns. (a) Initiates at puberty Initiates at foetal stage. 3 Marks Questions (b) Spermatozoa 1 egg and 3 polar 68. Germ cells divide mitotically to form large bodies. number of oogonia. This occurs in the embryonic stage. All oogonia are formed before birth. 55. Site–GnRH–pituitary gland Oogonia grow in size and form primary oocytes. FSH–Seminiferous tubules. Primary oocyte undergoes first meiotic division GnRH–stipulates the formations of LH and FSH which is completed just before ovulation forming a larger secondary oocyte and a smaller polar stimulates spermatogenesis. body. Secondary oocyte undergoes second meiotic division which is completed only when the sperm 56. Corpus luteum is formed after ovulation. gains entry into the oocyte forming a larger egg It regresses when fertilization does not occur. cell and a smaller polar body. 57. Muscular layer is myometrium, Glandular layer Chromosomes Oogonia is endometrium. Endometrium undergoes cyclic number per cell changes. Progesterone is required to maintain Mitosis this layer. differentiation 58. LH, FSH for ovulation 46 Fetal life Primary oocyte Progesterone for development of corpus luteum 59. Fimbrae → Infundibulum → Ampulla → 1st meiotic Ampulla-Isthmus Junction. Birth division Childhood (completed 60. Blastula Puberty prior to ovulation) Inner cell mass 23 First Secondary oocyte 23 polar body Trophoblast Adult Ovum reproductive life Second Trophoblast: Helps in attachment of blastula in polar body endometrium of uterus. 69. Target cells of lutenising hormone in males Inner cell mass: Differentiates into an embryo. are leydig cells. This hormone stimulates leydig cells to secrete male androgen, 61. (a) 1 (b) 8 – 16 (c) 32 testosterone which in turn initiates the process of spermatogenesis. In females, LH stimulates 62. Blastula (Blastomere). Cells of blastomere arrange follicles to release ovum, this is responsible themselves in outer layer called trophoblast and for ovulation, and formation of corpus luteum. Corpus luteum secretes progesterone. inner cell mass. Blastocyst reaches uterus, trophoblast attaches to uterus gets interdigitated endometrium grows and covers the blastocyst. 54 Biology–12

70. Blood Primary Tertiary follicle of additional sperms by blocking their entry. vessels follicle showing antrum This ensures the entry of one sperm only. Graafin follicle (ii) Plasma membrane (i) Ovum Ovum (iii) Zona pellucida Corpus luteum Structure of Human Ovum Sectional view of Human ovary 78. Refer answer no. 47. 71. Foetus signals pituitary (called foetal ejection 79. For diagram refer answer no. 47. reflex) → induces pituitary to secrete oxytocin → Functions: oxytocin increases the frequency of contraction of (a) Acrosome: The secretion of the acrosome uterine muscles → it induces further increases in the production of oxytocin by pituitary → cycle help the sperm enter into the cytoplasm of continues → foetus expelled out. the ovum through the zona pellucida and the plasma. 72. For diagram refer answer no. 70. 73. Inner layer of uterus is endometrium which is (b) Nucleus: It stores the genetic information, which is passed to next generation, it is also glandular in nature. During menstrual cycle, the responsible for determination of sex in a child. endometrium prepares itself for implantation. Implantation occurs if fertilization occurs, and (c) Middle piece: It contains mitochondrion if not, the endometrium breaks down. which provides energy for the movement of sperms. Middle wall is myometrium which is muscular layer and made up of smooth muscles. It contracts 80. (a) Seminal vesicle: Secretion of seminal during child birth to expel foetus when fully vesicle makes the part of seminal mature. plasma which is rich in fructose, calcium and some enzymes. It provides nutrients 74. Spermatozoa to the sperms. Spermatid (b) Scutellum: Helps in absorption of degraded material during germination from the Secondary endosperm. spermatocyte (c) Acrosome: Refer answer no. 79 (a) Primary 81. (a) During 13–15 days, FSH stimulates the spermatocyte ovarian follicle to secrete estrogens that Sertoli cell further stimulate the proliferation of the endometrium of the uterine wall. On 14th Spermatogonium day, LH surge causes ovulation. Graafian follicle ruptures to release ovum. Section view of Seminiferous Tubule (b) From 16 to 23 days, the corpus luteum 75. (a) X–Testicular lobule, location-scrotum. secretes progesterone which is required (b) Y–Seminal vesicles secretes seminal plasma. for the maintenance of endometrium. (c) Z–Epididymis, function–storage of sperm. In the absence of fertilisation, corpus 76. (a) In a new born baby, the gamete is primary luteum degenerates causing disintegration of endometrium leading to menstruation that oocyte and is present in ovary X. takes 3–5 days. Estrogen level is low from (b) Y is fimbrae on fallopian tubules. It collects 16-23 days, progesterone level increases. released ovum and sends it to fallopian tube. (c) During 24 to 29 days (luteal phase of 15 to (c) Z is ampullary isthumus junction of fallopian 28 days), the luteinising hormone (LH) is secreted by the anterior lobe of the pituitary tube. Fertilization takes place if sperm and gland. LH causes ovulation. The remaining ovum reach here simultaneously. cell of the ovarian follicles are stimulated 77. F u n c t i o n o f z o n a p e l l u c i d a : A f t e r o n e by the LH to develop corpus luteum. The sperm enters the ovum, the zona pellucida corpus luteum secretes large amount of undergoes changes and prevents the entry progesterone. Progesterone stimulates the uterine glands to produce increased amount Human Reproduction  55

of watery mucus. During the secretory 89. Sertoli cells Leydig cells phase, there is also similar increase in the secretion of watery mucus by the vaginal Location: seminiferous Interstitial space of glands and by the glands of the Fallopian tubes. Progesterone is also essential for tubule testes maintenance of the endometrium which is necessary for implantation of the fertilised F u n c t i o n : P r o v i d e Secrete male androgen- ovum and other events of pregnancy. In the absence of fertilisation, the corpus luteum nutrition to male germ testosterone degenerates. This causes disintegration of the endometrium leading to menstruation cells marking a new cycle. Endometrium of uterine wall breaks and menstrual cycle begins. 90. Refer answer no. 47 82. (a) From 8–12 days (follicular phase), the 91. Refer answer no. 47 for diagram (label only level of gonadotropins (LH and FSH) following parts) increase gradually and stimulate follicular development as well as secretion of estrogens Middle piece-Mitochondria provides energy for by growing follicles. movement (b) From 13 to 15 days, the endometrium becomes Tail helps in movement of sperm in vagina to thicker by rapid cell multiplication and reach egg for fertilization. there is increase in uterine glands and blood vessels. 92. Hormonal control of spermatogenesis in human males: (c) After ovulation, the remaining cells of the ovarian follicles are stimulated by LH to (i) Gonadotropin Releasing Hormone (GnRH) develop corpus luteum. releases from the hypothalamus during puberty. 83. (a) Blastocyst (ii) GnRH stimulates anterior pituitary to secrete (b) ‘A’ represents trophoblast, it attaches to gonadotropins, i.e. LH and FSH or Interstitial uterus and develops chorionic villi and later Cell Stimulating Hormone (ICSH). forms placenta. (iii) Leuteinising Hormone (LH) acts on Leydig cells to (c) Inner cell mass develops into three germ stimulate synthesis and secretion of androgens, layers: ectoderm, endoderm and mesoderm. which stimulates the process of spermatogenesis. (d) Stem cells are present in inner cell mass. (iv) Follicle Stimulating Hormone (FSH) acts on 84. Stage of human embryo at which it gets implanted Sertoli cells and stimulates them to secrete is blastocyst. certain factors which are necessary for the For the process of implantation refer answer no. 62. process of spermiogenesis. 85. During awareness programme the prominence 93. Refer answer no. 92 will be given to explain the process of sex determination in humans. Females are never Spermatogonia At Puberty Chromosomes responsible for giving birth to a female child number per cell because if sperm with X chromosome fuses with Mitosis differentiation egg then female child will develop from zygote 46 and if Y chromosome fuses with egg then male child will develop. The second X chromosome and Primary spermatocytes Y chromosome always comes from father and not from mother. 1st meiotic division 86. (a) Zygote after first cleavage Secondary spermatocytes 23 2nd meiotic division Spermatids 23 Differentiation (b) Morula stage Spermatozoa (a) GnRH or gonadotropin release hormone (c) Blastocyst stage Inner cell Trophoblast initiates spermatogenesis in humans. 87. For diagram refer answer no. 60. Process of spermatogenesis: Male germ cell 88. Refer answer no. 74. (spermatogonium) → mitosis → primary spermatocyte → meiosis–I → secondary spermatocyte → meiosis–II → spermatids → spermiogenesis → spermatozoa → spermiation (release of spermatozoa from seminiferous tubule) 94. Refer answer no. 70. 95. Sperm mature and become motile when the secretion of epididymis, vas deferens, seminal vesicle and prostate is poured in the common ejaculatory duct. 56 Biology–12

96. The hormones and their respective functions of the given glands are as follows: Glands/stages Hormones involved Functions 1. Hypothalamus Gonadotropin Releasing Stimulates the anterior pituitary to secrete luteinising hormone (GnRH) hormone (LH) and Follicle stimulating hormone (FSH). 2. Pituitary LH and FSH FSH stimulates the growth of the ovarian follicles and division of primary oocyte within the follicle to form secondary oocyte. It also stimulates the formation of estrogens. 3. Ovary Estrogen and progesterone Estrogen stimulates the proliferation of endometrium of the uterine wall. Progesterone is essential for the maintenance of endometrium for implantation and other events of pregnancy. 97. Corpus luteum degenerates when ovum is not fertilized. Due to this the progesterone level suddenly falls and endometrium lining is disintegrated leading to menstruation. 98. (a) Follicular phase Luteal phase Next cycle begins Day 6-15 Day 16 – 26 Day 26-28 • LH and FSH gradually • LH and FSH decreases • If no fertilization, corpus luteum increases • Corpus luteum secretes degenerates • Estrogen is produced by progesterone • Progesterone level falls suddenly ovary • Uterine wall grows and is • Uterine wall breaks • Uterine wall is repaired ready for implantation • Bleeding starts and next cycle begins (b) Source of hormones–Ovary for Estrogen and Progesterone 99. (a) & (b) Refer answer no. 37. 100. Pituitary FSH LH Hormone levels Days 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29/1 Menstruation Follicular phase Ovulation Luteal phase Next cycle begins Day 27-29 Day 1-5 Day 6-13 Day 14-15 Day 16 – 26 • If no fertilization, • Starts with first • LH and FSH • LH and FSH • LH and FSH corpus luteum day of bleeding gradually is very high, decreases degenerates increases causes ovulation • Progesterone level • Lasts for 3-5 days • Estrogen is • Estrogen is at • Corpus falls suddenly produced by ovary peak luteum secretes • Uterine wall breaks progesterone • Bleeding starts and • Endometrium • Uterine wall is • Endometrium • Uterine wall next cycle begins breaks down, repaired lining is grows and blood along with growing is ready for unfertilized implantation ovum flows out of vagina Human Reproduction  57

101. During fertilization, sperm comes in contact with zona pellucida of ovum → Induces changes in membrane and blocks the entry of other sperms → Sperm enters the cytoplasm of ovum through zona pellucida and plasma membrane with the help of enzymes of acrosome → Nucleus enters the cytoplasm of ovum → This initiates the completion of 2nd meiotic division → Haploid ovum and second polar body is formed → Two nuclei fuse and zygote is formed. Repeated mitosis occurs in zygote, morula is formed with 8-16 cells, each cell is called blastomere → Blastomere are rearranged, outer layer trophoblast and inner cell mass is formed → Blastocyst reaches uterus, trophoblast attaches to uterus, endometrium grows and covers the blastocyst, this is called implantation. It is the beginning of pregnancy. 102. Refer answer no. 101. 103. Acrosome (Function: enzymes help in fertilizing ovum) Middle piece (Function: it contains mitochondrias, which provide energy for the movement of sperm) Tail (function: helps sperm to move in the female reproductive tract to reach ovum) 5 Marks Questions (iii) Junction 104. (a) Ampulla Isthmus (iv) Endometrium (i) Uterus Myometrium Ovary Perimetrium (ii) Fimbriae (b) Refer answer no. 96. 105. (a) Oogenesis begins at the embryonic stage and the first meiotic division gets completed just prior to ovulation which happens once puberty is attained whereas spermatogenesis is initiated after puberty is attained. (b) Refer answer no. 70. 106. (a) Human male reproductive system 58 Biology–12

(b) S. No. Vas deferens Vasa efferentia (i) A connecting tube which carries spermatozoa It carries spermatozoa from rete testes to from epididymis to penis epididymis. S. Spermatogenesis Spermiogenesis No. (ii) • Process of formation of sperms from male • Process of formation of motile sperm from germ cells. non-motile spermatid. • Male germ cells are diploid from which • Spermatid and sperms, both are haploid. haploid sperms are formed. • Each male germ cell gives rise to four • One spermatid give rise to one sperm. spermatozoa. 107. Refer table, answer no. 100 Pituitary FSH LH Hormone levels Developing follicle Mature follicle Developing corpus luteum Regressing Ovarian events corpus luteum Ovarian Ovulation Hormone levels Estrogen Progesterone Uterine Menses events Days 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29/1 108. (i) Leydig cells: Lie in the space between provides nutrition and energy for sperm seminiferous tubule in testes. They secrete male androgens, testosterone. motility. (ii) Sertoli cells: Lie in seminiferous tubule. They Bulbourethral gland: Secretion of these provide nutrition to male germ cells and developing sperms. glands helps in lubrication of penis. (iii) P r i m a r y s p e r m a t o c y t e s : P r e s e n t i n 109. Primary oocytes are formed in foetal ovary. seminiferous tubule in testes, they undergo meiotic division and give rise to secondary Refer answer no. 68. spermatocyte which in turn modifies into spermatozoa. Hormones involved Male accessory glands are seminal vesicle, (i) Gonadotropin Releasing Hormone (GnRH) prostate gland, bulbourethral gland. (ii) Luteinising Hormone (LH) Seminal vesicle: The secretion of these glands makes seminal plasma which contains (iii) Follicle Stimulating Hormone (FSH) fructose, calcium and some enzymes. It OR Role of gonadotropins: Follicle stimulating hormone and luteinising hormone are secreted by anterior pituitary gland during follicular phase of menstrual cycle. The oogonia differentiates into graafian follicle. Human Reproduction  59

Chromosomes Oogonia 113. (a) Spermatogenesis occurs in seminiferous number per cell tubules of the testes. Mitosis differentiation (b) Seminiferous tubule Rete Testis vasa efferentia→ Epididymis → Vas deferens → 46 Foetal life Primary oocyte Ejaculatory duct 1st meiotic 114. division Ovulation GnRH LH & FSH Birth (completed Childhood Pregnancy lactation Progesterone 23 Puberty prior to First ovulation) Secondary oocyte polar body Placenta Foetal growth Adult Ovum 23 reproductive Second Chorionic gonadotropin life + lactogen polar body Parturition Oxytocin On 14th day the FSH and LH level is at its peak. This causes the rupture of the graafian follicle 115. Refer answer no. 106. and ovum is released. 116. Refer answer no. 106 117. (a) ‘F’ illustrates ovulation. This stage is 110. (a) GnRH or gonadotropin release hormone initiates spermatogenesis in humans. ovulation. Process of spermatogenesis: Male germ cell (b) Estrogen is released during ovulation from (spermatogonium) → mitosis → primary ovary, Follicle stimulating hormone and spermatocyte → meiosis–I → secondary luteinizing hormone is released from pituitary spermatocyte → meiosis–II → spermatids gland during ovulation. → spermiogenesis → spermatozoa → spermiation (release of spermatozoa from (c) The endometrium layer prepares itself for seminiferous tubule) implantation, it gets thickened and the blood supply of endometrium increases. (b) For diagram refer answer no. 47. Label only (i) Acrosome ( ii) Mitochondria (iii) Tail (d) C H 111. Difference: • It represents • It represents secondary follicle corpus luteum Oogenesis Spermatogenesis • In this process ovum • I n t h i s p r o c e s s • Ovum is surrounded • Granulosa layer is formed. sperms are formed. by layers of granulosa absent. cells. • O o g e n e s i s s t a r t s • S p e r m a t o g e n e s i s b e f o r e b i r t h a n d starts at puberty and • Theca is present • Theca absent remains continuous remains continuous till menopause. during lifetime. • No yellow coloured • Yellow coloured • Unequal division of • After meiosis, four body body meiosis occurs and spermatozoa are only one functional formed and all are • No progesterone • Secretes o v u m o r e g g i s functional. secreted progesterone formed, other three act as polar bodies (e) Corona radiate which are very small Plasma membrane and non-functional. Nucleus (haploid) 112. Refer answer no. 108. Cytoplasm Zona pellucida Spermatogonia At Puberty Chromosomes Structure of Human ovum before fertilization number per cell Mitosis differentiation 118. For diagram refer answer no. 42. 46 For ovarian events refer answer no. 100 table. 119. Fertilization: For events of fertilization and Primary spermatocytes 1st meiotic division implantation refer answer no. 101. Secondary spermatocytes 23 Role of placenta as an endocrine gland: 2nd meiotic division Placenta secretes the following hormones. Spermatids 23 Differentiation Spermatozoa 60 Biology–12

Human chorionic gonadotropin (hCG) gametogenesis gets completed in follopian  Human placental lactogen (hPL) tube (Ampullary-Isthmus Junction) just after  Estrogen the nucleus of sperm enters ovum.   Progesterone These hormones are essential for normal foetus 130. Refer answer no. 70 and for events of oogenesis development and maintenance of pregnancy. refer answer no. 108. 120. Site of fertilization-Ampullary isthmus junction in fallopian tube 131. (a) X–Leutinizing hormone (Follicular phase) Events that follow fertilization: Refer answer Y–Follicle stumulating hormone. no. 101. 121. R e f e r t e x t f o r f e r t i l i z a t i o n p r o c e s s o n (b) (i) Follicle development takes place (Follicular Refer answer no. 101. Phase) Inner cell mass (ii) Ovulation Trophoblast (iii) Corpus luteum is formed which secretes progesterone (Luteal phase) (c) (i) FSH stimulates the development of Blastocyst follicles into mature graafin follicles 122. (a) Refer answer no. 70. (ii) LH and FSH are at low level. Corpus (b) Refer answer no. 106 & 96 luteum secretes progesterone. Which is 123. (a) Refer answer no. 108. essential to maintain endometrium. (b) Refer answer no. 110 124. Refer answer no. 47 for diagram. 132. (a) Refer answer no. 101. Refer answer no. 79 & 91. (b) Refer answer no. 60. 125. (a) Refer answer no. 68. 133. (a) Entry of sperm nucleus in egg induces the (b) completion of meiotic division of secondary Sperm oocyte Zona Ovum Cells of the (b) Refer answer no. 101. Pellucida corona radiata 134. (a) Zona pellucida (b) Refer answer no. 6. Perivitelline space (c) It occurs at Ampullary Isthmus Junction. Ovum surrounded by few sperms (d) Repeated mitotic divisions occur in zygote 126. (a) Refer answer no. 110. and the stage with 8–16 blastomeres is called (b) Refer answer no. 47. morula. 127. (a) Refer answer no. 47. 135. (a) (i) Menstrual phase - first 3-5 days of the cycle (b) Refer answer no. 79 & 91. where menstrual flow occurs due to break down of endometrial lining of uterus, if 128. Refer answer no. 68. the released ovum is not fertilised. 129. (a) Refer answer no. 110. (b) Refer answer no. 17. (ii) Follicular phase - from 5th to 14th day of the cycle where the primary follicles grow (c) Gametogenesis gets completed in testes to become a fully mature Graafian follicle, in human males and in human females endometrium of uterus regenerates, Graafian follicle ruptures to release ova (ovulation on 14th day) (iii) Luteal Phase - During 15th to 28th day remaining parts of graafian follicle transform into corpus luteum, secretion of progesterone (essential for maintenance of endometrium). All these phases are under the influence of varying concentrations of pituitary and ovarian hormone (b) Yes, can take appropriate precautions between 10th to 17th day of the menstrual cycle when the chances of fertilisation are high. Human Reproduction  61

136. (a) Refer answer no. 100 and 107. called as fertile period. If a person avoids (b) It is clear in the above table that the coitus during this period, the unwanted pregnancies can be avoided. ovum is released during 10-17 days during menstrual cycle. This period is Assertion & Reason Type Questions For question numbers 1-15: Two statements 8. Assertion (A): The second meiotic division of the are given one labelled Assertion (A) and the other developing ovarian follicle is completed just after labelled Reason (R). Select the correct answer to these conception. questions from the codes (a), (b), (c) and (d) as given below. Reason (R): Conception is the onset of pregnancy when the implantation of blastocyst take place. (a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion. 9. Assertion (A): At the time of implantation, which takes place in 14 days, the human embryo (b) Both Assertion and Reason are true but Reason is called blastocyst. is NOT the correct explanation of Assertion. Reason (R): Implantation occurs in the gastrula (c) Assertion is true but Reason is false. stage. (d) Assertion is false and Reason is also false. 1. Assertion (A): In human male, testis are extra 10. Assertion (A): If several spermatozoa hit the egg at the same time, all can enter the egg. abdominal and lie in scrotal sacs. Reason (R): The above process is called Reason (R): Scrotum acts as thermoregulator amphimixis which can be prevented by and keeps testicular temperature lower by 2°C fertilisation membrane. for normal spermatogenesis. 11. Assertion (A): Corpus luteum contains blood 2. Assertion (A): At puberty human male develops clot and fibrin. secondary sexual characters. Reason (R): Corpus luteum is formed by the Reason (R): At puberty there is decreased germinal epithelium. secretion of testosterone in male. 12. Assertion (A): Placenta acts as a major 3. Assertion (A): Cilia, lining the fallopian tube, endocrine organ. helps to pick up and push the released ovum into the oviduct. Reason (R): In mammals fetal components of the placenta derive initially from the chondroblast. Reason (R): Cilia of fallopian tubes beat towards uterus. 13. Assertion (A): In mammals the female secondary sexual characters are developed by gonadotropins. 4. Assertion (A): Corpus luteum secretes the female hormone progesterone. Reason (R): Gonadotropins are secreted by Graafian follicle. Reason (R): After ovulation, a ruptured follicle turns into yellowish solid mass of cells called 14. Assertion (A): Head of sperm consists of corpus albicans. acrosome and mitochondria. 5. Assertion (A): Epididymis is divided into three Reason (R): Acrosome contains spiral row of parts. mitochondria. Reason (R): Epididymis is the organ that stores 15. Assertion (A): The inner cell mass of blastocyst spermatozoa. gets attached to the endometrium during embryonic developed in humans. 6. Assertion (A): One oogonium produces one ovum and three polar bodies. Reason (R): The blastomeres in the blastocyst not gets arranged into trophoblast and inner cell Reason (R): Polar bodies have small amount of mass.[CBSE 2022] cytoplasm. 1. (a) Answers 5. (b) 7. Assertion (A): In morula stage, the cells divide 6. (b) 10. (d) without any increase in size. 11. (c) 2. (c) 3. (a) 4. (c) 15. (d) 7. (b) 8. (b) 9. (d) Reason (R): Zona pellucida remains undivided 12. (c) 13. (d) 14. (d) till cleavage is complete. 62 Biology–12

Case Based Questions 1. Human male reproductive system comprises of (b) Both assertion and reasons are true but a pair of testes, primary sex organs associated reason is not the correct explanation of with formation of gametes and production of sex assertion. hormone. Study the given figure of human male reproductive system and answer the following (c) Assertion is true but reason is false questions. (d) Both assertion and reason are false. Q T 2. Spermatogenesis is the production of sperms R from male germ cells (spermatogonia) inside the testes (seminiferous tubule). This process begin S at puberty. Observe the following flow diagram and answer the questions that follows: P Spermatogonia ↓ Mitosis and differentiation Primary spermatocyte ↓ 1st meiotic division Secondary spermatocyte (i) Which of the following is correct for labelled ↓ 2nd meiotic division part P? Spermatids (a) P is rete testis which transports sperms to outside. ↓ Differentiation (b) P is epididymis which secretes fluid that Spermatozoa nourish the sperms (i) This happens during spermatogenesis (c) P is epididymis that carry sperm and secretion of seminal vesicles (a) Meiosis (b) Mitosis (d) P is rete testis which lies along inner side (c) Meiosis and mitosis (d) None of these. of each testis and stores the sperms (ii) The process of spermatogenesis is induced by (ii) Identify the correctly matched pair. (a) TSH (b) FSH (a) Q – Vasa efferentia (c) MSH (d) ACTH (b) R – Ejaculatory duct (iii) The number of spermatozoa, a single primary spermatocyte finally produced in (c) S – Seminal vesicle spermatogenesis is (d) T – Bulbourethral gland (iii) Which statement is incorrect for Q? (a) 2 (b) 4 (a) It carries spermatozoa from epididymis (c) 6 (d) 8 to ejaculatory duct (iv) In spermatogenesis, the phases of maturation (b) Q are only 2 in number involve (c) It arises from rete testis (a) formation of spermatids from primary spermatocyte through meiosis. (d) It constitutes male sex accessory duct (iv) Which structure passes through the prostate (b) growth of spermatogonia into primary gland and carries sperms and secretion of spermatocytes. seminal vesicle? (c) formation of spermatogonia from gonocytes (a) P (b) T through mitosis. (c) S (d) R (d) formation of oogonia from spermatocyte through meiosis. (v) Assertion: Mucus present in secretion of bulbourethral gland decreases the number of sperms damaged during ejaculation. (v) The correct sequence of cell stage in spermato- genesis is Reason: Mucus lubricates the end of penis and lining of the urethra. (a) s p e r m a t o c y t e → s p e r m a t i d s → spermatogonia → spermatozoa (a) Both assertion and reason are true and reason is the correct explanation of (b) s p e r m a t o g o n i a → s p e r m a t i d s → assertion. spermatocyte → spermatozoa Human Reproduction  63

(c) spermatocytes → spermatogonia → (b) Primary follicle changes into Graafian spermatid → spermatozoa follicle. (d) spermatogonia → spermatocytes → (c) Endometrium rebuilds and estrogen spermatids → spermatozoa secretion increases 3. The first menstruation is called menarche, that (d) LH surge inducing release of an ovum. usually occurs between 12 and 15 years. In (iv) Identify the hormones that attain peak level human females, menstruation is repeated at during ovulatory phase. an average interval of about 28129 days and is (a) FSH called menstrual cycle. It is regulated by certain (b) Progesterone hormones, as pituitary gland is stimulated by (c) LH releasing factors produced in the hypothalamus. (d) Both (a) and (c) The hormones produced by pituitary gland (v) Withdrawal of which hormone causes degeneration of corpus luteum? influence the ovaries. The hormones secreted by the ovaries affect the walls of the uterus. (a) FSH (i) T h e b r e a k d o w n o f e n d o m e t r i u m i s (b) LH characteristic of (c) Progesterone (d) Estrogen (a) proliferative phase (b) luteal phase A ns. 1. (i) (b) (ii) (b) (c) ovulatory phase (d) menstrual phase (iii) (c) (iv) (d) (ii) Which days of the menstrual cycle marks the (v) (a) proliferative phase? 2. (i) (c) (ii) (b) (a) 1-5 (b) 15-28 (iii) (b) (iv) (a) (c) 6-13 (d) 10-14 (v) (d) (iii) Which of the following occurs during secretory 3. (i) (d) (ii) (c) phase? (iii) (a) (iv) (d) (a) Empty Graafian follicle changes into (v) (b) corpus luteum. qqq 64 Biology–12

3 Reproductive Health Topics Covered 3.2 Population Explosion and Birth Control 3.4 Sexually Transmitted Diseases (STDs) 3 .1 Reproductive Health–Problems and Strategies 3 .3 Medical Termination of Pregnancy (MTP) 3.5 Infertility C hapter map REPRODUCTIVE HEALTH Sexually Transmitted Birth Control Methods Assisted Reproductive Diseases (STDs) Technologies (ARTs) Temporary Permanent • In vitro Fertilisation • AIDS Methods Methods (IVF) • Genital Herpes • Zygote Intra Fallopian • Genital Warts Transfer (ZIFT) • Hepatitis-B • G amete Intra Fallopian • Gonorrhoea Transfer (GIFT) Natural Barrier Intrauterine Sterilisation method method Devices Implant (Essure) Periodic Chemical Mechanical Oral Hormonal Vaginal Tubectomy abstinence/ barrier barrier contraceptives barrier Ring Non- Vasectomy rhythm Medical method medicated IUDs Termination of Continuous Foaming Condom Mini pills, Subcutaneous Pregnancy (MTP) abstinence tablets, Diaphragm Saheli Implants Hormonal melting releasing Progestasert Coitus supposito- (centchro- LNG - 20 interruptus ries, jellies man) IUDs and creams Copper Cu T-380 A, releasing Nova T, Cu Lactational IUDs 7, CuT380 Ag Amenorrhoea Multiload 375 Reproductive health according to World Health Organization (WHO) is defined as the total well being in all aspects of reproduction, i.e., physical, emotional, behavioural and social. Topic 1. Reproductive Health–Problems and Strategies • Indian Government had initiated the programme of family planning in 1951. The aim of this programme was: To attain total reproductive health in the country 65

To achieve stable population size Post natal care of both mother and child Reduce the death rate of mother and child Importance of breast feeding To improve overall health in terms of reproduction Curbing dwindling sex ratio • Reproductive and Child Health Care (RCH) Benefits of having small family programme was launched in 1997. Its aim was: Prevention of sexual abuse and other sex related To create awareness about reproduction among crimes people • Government can successfully implement such plans To provide facilities for maintaining reproductive by: health Developing infrastructure and easy availability of To provide support to the society to become experts and materials reproductively healthy. P r o v i d i n g m e d i c a l a s s i s t a n c e t o p e o p l e • Use of print and audio-visual media, government during pregnancy, delivery, STDs, abortions, and non-governmental agencies are also creating contraception, menstrual problems and infertility. awareness among people for reproduction related matters. New strategies should be implemented from time to time for efficient care. • A socially responsible and healthy society can be built by providing correct information to the • People tend to misuse the new technology used children about: for benefit of society such as amniocentesis. This test is used to check any type of abnormality in Reproductive organs developing embryo but people mostly use it for sex determination. To stop female foeticide, government Adolescence and related changes of India has put statutory ban on this technique. Safe and hygienic practices of sex • It is only when the people of a society are aware about above stated sex related issues, medical Sexually transmitted diseases like AIDS facilities and better maternal and post natal care, the society can be reproductively healthy. Discourage misconceptions • An Indian institute, Central Drug Research • In adults, information can be provided about: Institute (CDRI), Lucknow has developed non-hormonal birth control pill known as Saheli. Birth control methods Care during pregnancy Topic 2. Population explosion and birth Control • Post independence, population increased manifolds. • Chances of fertilization in lactating mother is It crossed 1 billion in May, 2000. Life expectancy negligible as there is no ovulation till six months of human being increased due to better medical from the birth of child. This is called lactational facilities. amenorrhea. • There was a decrease in mother and child death • Barrier methods prevent the sperm to meet ovum during birth, and the number of individuals at physically. These are available both for males and reproductive age increased. This led to population females. Mostly these barriers are made up of rubber explosion. or latex sheath which are used to cover the male penis or vagina/cervix in females. • Apart from some measures taken by government to create awareness for small families, encouraging • Barrier methods such as condoms for males, various contraceptive methods can also help to diaphragms, cervical caps and vaults for females control it. can be effectively used to physically prevent sperm to fertilize ovum. “Nirodh\" was popular condom used • Contraceptive methods help one to prevent unwanted for family planning in India. pregnancies. Contraceptive methods are: • A couple can avoid coitus during fertile period i.e. Condom for male Condom for female 10-17th day of menstrual cycle. This reduces chance of fertilization. It is called periodic abstinence. • Spermicidal creams, jellies and foams can also be used to increase the efficiency of barrier methods. • In withdrawal or coitus interruptus, the male partner withdraws his penis from vagina just before ejaculation 66 Biology–12

• One of the most used contraceptive method, Intra • A non-hormonal birth control pill ‘Saheli’ is to be Uterine Devices (IUDs) are inserted in uterus of consumed once in a week. female through vagina. • Implants are the devices which are implanted under • IUDs are of following types: skin and function similar to oral pills. Non-medicated IUDs (e.g., Lippes loop), Copper releasing IUDs (CuT, Cu7, Multiload • Surgical methods are irreversible and permanent 375) method of contraception in both males and females. • In males, vasectomy is done in which a part of vas deferens is removed and ends are tied. Copper T (CuT) Vasectomy Hormone releasing IUDs (Progestasert, LNG- • In female, tubectomy is done in which a part 20) of fallopian tube is removed and the cut ends are tied. • IUDs increase phagocytosis of sperms within the uterus, copper ions released suppress sperm motility Tubectomy and the fertilizing capacity of sperms. The hormone releasing IUDs make the uterus unsuitable for implantation and the cervix hostile to the sperms. • Another method is the use of Oral contraceptives or birth control pills. These pills which are available in the form of tablets are made up of progestogens or combination of progestogens and estrogens. They should be taken daily during menstrual cycle for 21 days. These pills inhibit ovulation and implantation and alter the quality of cervical mucus to prevent or retard entry of sperms. • The advantage of such pills is that they are easily available, low cost and effective contraceptive with fewer side effects. Topic 3. Medical Termination of Pregnancy (MTP) • Medical termination of pregnancy is also called • To avoid such illegal practices, counselling about induced abortion. It is intentional removal of foetus risks involved should be done. Unprotected before the full term pregnancy is over. intercourse should be avoided and more health care facilities should be provided. • It was only in 1971, Government of India declared MTP legal but with strict conditions to prevent • There must be statutory ban on Amniocentesis misuse of this technique for female foeticide. (a foetal sex determination test based on the chromosomal pattern in the amniotic fluid • MTPs are allowed in case where continuing with surrounding the developing embryo) for sex pregnancy could be fatal either to mother or foetus determination to legally check increasing female or both. foeticides. • The procedure is safe for mother during first trimester only, mostly it is performed by quacks and is unsafe and fatal. Reproductive Health  67

Topic 4. Sexually transmitted Diseases (STDs) • Diseases which are transmitted through sexual • Common symptoms for such diseases are itching, intercourse are called sexually transmitted diseases. fluid discharge, pain, swelling in genital region. These are also called as Venereal Diseases (VD) or Reproductive Tract Infections (RTI). • If not treated, other complications like abortion, still births, ectopic pregnancy, infertility, pelvic • AIDS, Gonorrhoea, syphilis, genital herpes and inflammatory diseases and even cancer of hepatitis-B are some common examples. AIDS, reproductive tract can appear. Hepatitis-B and genital herpes are the diseases which cannot be cured fully. Others can be cured if Sexually transmitted diseases can be avoided by detected early. adopting some preventive measures like: • Apart from sexual contact, such diseases are • Avoid sex with unknown partners/multiple partners. also transmitted via infected needles, surgical instruments, blood transfusion and from infected • Use condoms during coitus. mother to her foetus. • If there is any doubt, one should go to doctor and get complete treatment if the disease is confirmed. Topic 5. Infertility • When embryo with more than 8 blastomeres is transferred to uterus, it is called Intra Uterine • It is a condition where a couple is unable to produce Transfer (IUT) children in spite of unprotected sexual co-habitation. • In Gamete Intra Fallopian Transfer (GIFT), • Reasons may be physical, congenital, due to some the egg from donor female is transferred to another disease, it can be hormonal imbalance or side effect female who cannot produce it but body is suitable of some disease, immunological or psychological. for fertilization and further development. • Both males and females can be responsible for • When sperm is directly injected in ovum it is called infertility but mostly females are blamed in our Intra Cytoplasmic Sperm Injection (ICSI) society. • In Artificial Insemination (AI), semen from donor • Assisted Reproductive Technologies (ART) or husband is artificially injected into vagina. are used to treat or overcome such defects. Various methods are used according to the condition of • In Intra Uterine Insemination (IUI) semen is couples. artificially injected into uterus. • In IVF or in vitro fertilization, the ova and sperm • Problems with such techniques are that they from couple or donors are taken and fertilization is involve much cost, less availability of facilities in induced under laboratory conditions similar to that our country, and some social factors like emotional, of human body. After fusion, zygote or embryo is religious beliefs does not allow people to adopt such transferred in female's body. methods. • When a zygote or an early embryo up to 8 blastomeres • Best method to have a child is adoption. is transferred to the fallopian tube, this procedure is called Zygote Intra Fallopian Transfer or ZIFT. EXERCISE I. Multiple Choice Questions (b) Result in decline in growth rate 1. The method of directly injecting a sperm into (c) Not cause significant change in growth rate (d) Result in an explosive population/exp ovum in assisted by reproductive technology is 3. Intensely lactating mothers do not generally called: conceive due to the: (a) GIFT (b) ZIFT (a) Suppression of gonadotropins (c) ICSI (b) Hyper secretion of gonadotropins (d) ET (c) Suppression of gametic transport 2. Decreased IMR and decreased MMR in a (d) Suppression of fertilization 4. Sterilisation techniques are generally fool proof population will: methods of contraception with least side effects. (a) Cause rapid increase in growth rate 68 Biology–12

Yet, this is the last option for the couples because: (b) Zygote is collected from a female donor and transferred to the fallopian tube (i) It is almost irreversible (ii) Of the misconception that it will reduce sexual (c) Zygote is collected from a female donor and urge/drive transferred to the uterus (iii) It is a surgical procedure (d) Ova collected from a female donor and transferred to the uterus (iv) Of lack of sufficient facilities in many parts of the country 12. The correct surgical procedure as a contraceptive method is: Choose the correct option: (a) Ovariectomy (b) Hysterectomy (a) (i) and (iii) (b) (ii) and (iii) (c) (ii) and (iv) (d) (i), (ii), (iii) and (iv) (c) Vasectomy (d) Castration 5. A national level approach to build up a 13. Diaphragms are contraceptive devices used by reproductively healthy society was taken up in the females. Choose the correct option from the our country in: statements given below: (a) 1950s (b) 1960s (i) They are introduced into the uterus (c) 1980s (d) 1990s (ii) They are placed to cover the cervical region 6. Emergency contraceptives are effective if used (iii) They act as physical barriers for sperm entry within: (iv) They act as spermicidal agents (a) 72 hrs of coitus (b) 72 hrs of ovulation (a) (i) and (ii) (b) (i) and (iii) (c) 72 hrs of menstruation (c) (ii) and (iii) (d) (iii) & (iv) (d) 72 hrs of implantation 14. Breast-feeding the baby acts as a natural 7. Choose the right one among the statements given contraceptive for the mother because it prevents: below: (i) Ovulation (ii) Menstruation (a) IUDs are generally inserted by the user herself (iii) Insemination (iv) Fertilisation (b) IUDs increase phagocytosis reaction in the uterus Choose the correct option: (c) IUDs suppress gametogenesis (a) (ii) and (iv) (b) (i) and (iii) (d) IUDs once inserted need not be replaced (c) (i) and (iv) (d) (i) and (ii) 8. Following statements are given regarding MTP. [CBSE 2022] Choose the correct options given below: 15. The given figure shows the different stages of (i) MTPs are generally advised during first human embryo: trimester (ii) MTPs are used as a contraceptive method (iii) MTPs are always surgical (iv) MTPs require the assistance of qualified medical personnel (a) (ii) and (iii) (b) (ii) and (iii) Identify the correct labellings for W, X, Y and (c) (i) and (iv) (d) (i) and (ii) Z and choose the correct option from the table 9. From the sexually transmitted diseases below: mentioned below, identify the one which does W XY Z not specifically affect the sex organs: (a) Syphilis (b) AIDS (a) Cleavage Blastocyst Morula Fertilisation (c) Gonorrhea (d) Genital warts (b) Blastocyst Morula Cleavage Fertilisation 10. C o n d o m s a r e o n e o f t h e m o s t p o p u l a r (c) Morula Cleavage Blastocyst Fertilisation contraceptives because of the following reasons: (d) Morula Blastocyst Cleavage Fertilisation (a) These are effective barriers for insemination [CBSE 2022] (b) They do not interfere with coital act 16. During human embryonic development the (c) These help in reducing the risk of STDs external genital organs are well developed in the (d) All of the above foetus by the end of 11. Choose the correct statement regarding the ZIFT (a) 6 weeks of pregnancy procedure: (b) 12 weeks of pregnancy (a) Ova collected from a female donor are transferred to the fallopian tube to facilitate (c) 18 weeks of pregnancy zygote formation. (d) 24 weeks of pregnancy [CBSE 2022] Reproductive Health  69

17. The accessory ducts in the human male 2 Mark Questions reproductive system consists of 7. Why are copper containing intrauterine devices (a) Epididymis, Prostrate, Rete testis considered an ideal contraceptive for human (b) Rete testis, Vas efferentia, Seminal vesicles females?  [Delhi 2014 C] (c) Vas efferentia, Bulbourethral, Epididymis 8. What do oral pills contain and how do they act as effective contraceptives? [All India 2014 C] (d) Rete testis, Epididymis, Vas deferens 9. Why is \"Saheli\" considered an effective [CBSE 2022] contraceptive for women to space children? 18. A specialised procedure to form an embryo in the [Delhi 2014 C] laboratory in which sperm is directly, injected into the ovum is 10. How do 'implants' act as an effective method of (a) IUT (b) IUI contraception in human females? Mention its one (c) ICSI (d) ZIFT advantage over contraceptive pills. [CBSE 2022] [Delhi 2012 C] 19. Listed below are all reproductive tract infections 11. At the time of Independence, the population of except India was 350 million, which exploded to over 1 (a) Genital herpes (b) Filariasis billion by May 2000. List any two reasons for this (c) Trichomoniasis (d) Syphilis rise in population and any two steps taken by the [CBSE 2022] government to check this population explosion. II. Fill in the Blanks [Foreign 2011] 1. Syphilis is caused by _____ and gonorrhoea is 12. Expand IUD. Why is hormone releasing IUD caused by ______ . considered as a good contraceptive to space 2. First test tube baby was born in ____ on July 25, children?  [AIl India 2008] 1978. 13. Why is CuT considered as a good contraceptive device to space children? [Delhi 2011] 3. Cervical caps and vaults are used ___ for conception. 14. After a brief medical examination a healthy couple came to know that both of them are unable 4. The oldest method of birth control is _____ . to produce functional gametes and should look for III. True or False an ART. Name the act and the procedure involved 1. Father is responsible for the sex of the child. 2. Vasectomy has ill effects on the sexual life of the that you can suggest to them to help them to bear male. a child.  [Delhi 2015] 3. Poverty and illiteracy play a major role towards 15. What is amniocentesis? How is it mis-used? the population explosion. [AIl India 2014 C] 4. MTP can be done at any stage of pregnancy. 16. Why there is a statutory ban on amni-ocentesis? 5. Saheli is a daily pill. Why is this technique so named?[Delhi 2012 C] 17. An infertile couple is advised to adopt test- 1 Mark Questions tube baby programme. Describe two principle 1. Mention one positive and one negative application procedures adopted for such technologies. of amniocentesis. [Delhi 2010] [Delhi 2012 C] 2. Mention any two events that are inhibited by 18. \"Intra-Cytoplasmic Sperm Injection\" and 'Gamete the intake of oral contraceptive pills to prevent Intra Fallopian Transfer' are two assisted pregnancy in humans.  [AIl India 2009] reproductive technology. How is one different 3. Why is Saheli a well-accepted contrace-ptive pill? from other? [AIl India 2014 C] [Foreign 2010] 19. Name any two assisted reproductive technologies that help infertile couples to have children. OR [Delhi 2012 C] Why do some women use Saheli pills? [All India 2009 C] 20. Expand: GIFT and ICSI. [All India 2012 C] 21. Why is ZIFT a boon to childless couples? Explain 4. Name the STDs which can be transmitted the procedure. [Delhi 2013 C] through contaminated blood.[AIl India 2009 C] 22. State any four methods to overcome infertility in 5. Name an IUD that you would recommend to human couples. [Delhi 2011 C] promote the cervix hostility to the sperms. [Delhi 2014 C] 3 Mark Questions 6. State one reason why breast-feeding the baby 23. (a) Mention the problems that are taken care acts as a natural contraceptive for the mother. of by Reproduction and Child Health Care Programme. [All India 2014 C] 70 Biology–12

(b) What is amniocentesis and why there is a 31. Name and explain the surgical method advised statutory ban on it? to human males and females as a means of birth [AIl India 2014, 2016, Foreign 2015] control. Mention its one advantage and one 24. Your school has been selected by the department disadvantage. [Foreign 2014] of education to organize and host an inter school 32. A pregnant human female was advised to undergo MTP. It was diagnosed by her doctor seminar on ‘reproductive health-problems that the foetus she is carrying has developed and practices’. However, many parents are from a zygote formed by an XX-egg fertilised reluctant to permit their wards to attend it. Their by Y-carrying sperm. Why was she advised to argument is that the topic is too embarrassing. undergo MTP? [Hots, All India 2010] Put forth four arguments with appropriate 33. A large number of married couples the world over reasons and explanations to justify the topic to are childless. It is shocking to know that in India be very essential and timely.  [All India 2015] the female partner is often blamed for the couple 25. Reproductive and Child Healthcare (RCH) being childless. programmes are currently in operation. One (a) Why in your opinion the female partner is of the major tasks of these programmes is to often blamed for such situations in India? create awareness amongst people about the (b) Mention any two values that you as a biology student can promote to check this social evil. wide range of reproduction related aspects. As this is important and essential for building a reproductively healthy society. (c) State any two reasons responsible for the cause of infertility. (a) “Providing sex education in schools is one of the ways to meet this goal.” Give four points (d) Suggest a technique that can help the couple in support of your opinion regarding this to have a child where the problem is with the statement. male partner.  [All India 2016] (b) List any two ‘indicators’ that indicate a 34. (a) Name any two copper releasing IUDs. reproductively healthy society. [Delhi 2016] (b) Explain how do they act as effective contraceptives in human female. 26. A mother of one-year-old daughter wanted to space her second child. Her doctor suggested CuT. [All India 2014] Explain its contraceptive actions.  [Delhi 2008] 35. A woman has certain queries as listed below, before starting with contraceptive pills, Answer 27. Describe lactational amenorrhea method of birth them: control.  [AIl India 2011] 28. If implementation of better techniques and new (a) What do contraceptive pills contain and how strategies are required to provide more efficient do they act as contraceptives? care and assistance to people, then why is there (b) What schedule should be followed for taking a statutory ban on amniocentesis? Write the use these pills? [All India 2014] of this technique and give reason to justify the 36. Suggest and explain any three Assisted ban.  [AIl India 2014, Foreign 2015] Reproductive Technologies (ART) to an infertile 29. (a) List any four characteristics of an ideal couple.[All India 2013] contraceptive. 37. Medically it is advised to all young mothers (b) Name two intrauterine contraceptive devices that breastfeeding is the best for their newborn that affect the mortality of sperms. babies. Do you agree? Give reasons in support of [AIl India 2016] your answer. [CBSE 2018] 30. Name two hormones that are constituents of 5 Mark Questions contraceptive pills. Why do they have high and 38. How are assisted reproductive techno-logies effective contraceptive value? Name a commonly helpful to humans? How are ZIFT and GIFT different from intra uterine transfers? Explain. prescribed non-steroidal oral pill. [Foreign 2009] [AIl India 2016] Answers I. Multiple Choice Questions 5. (a) II. Fill in the Blanks 1. (c) 2. (a) 3. (a) 4. (d) 10. (d) 1. treponema pallidum, neisseria gonorrhae 6. (a) 7. (b) 8. (c) 9. (b) 15. (c) 2. England 11. (b) 12. (c) 13. (c) 14. (d) 3. barriers 16. (b) 17. (d) 18. (c) 19. (b) 4. coitus interruptus Reproductive Health  71

III. True or False (ii) Statutory raising marriageable age of female to 18 years and of males to 21 years. 1. True 2. False 3. True 4. False 5. False 12. Intra uterine device. 1 Mark Questions H o r m o n e r e l e a s i n g I U D r e d u c e s s p e r m 1. Positive application of amniocentesis: This mobility and make uterus unsuitable for technique is used to find out chromosomal implantation. abnormality in developing foetus. 13. CuT is non-hormonal, non-medicated IUD which releases copper ions. Copper ions suppress the Negative application of amniocentesis: This sperm motility and fertilizing capacity of sperms. technique is used to find out sex of foetus which It also increases the phagocytosis of sperms. leads to female foeticide. 14. Act name is Zygote Intra Fallopian transfer 2. (i) Contraceptive pills inhibit the secretion of FSH (ZIFT). The sperm and eggs are collected from and LH which leads to inhibition of ovulation donors and fertilized in vitro. The zygote or early from ovary. embryo till 8 blastomeres is then transferred to fallopian tube of mother for further development. These pills inhibit implantation. It makes cervix hostile and inhibits sperm to enter into uterus. 15. Amniocentesis is a test is used to check any type of abnormality in developing embryo. It is 3. Saheli is non-steroidal and non-hormonal being misused for sex determination by some contraceptive pill and has no or minimum side irresponsible people. effects. 16. To stop female foeticide, Government of India 4. AIDS (Acquired Immuno Deficiency Syndrome) has put statutory ban on amniocentesis. It is 5. Hormone releasing IUD, Progestasert, LNG-20. named so because foetal cells from amniotic fluid 6. There is no menstruation during breast feeding, is taken and cultured to check any abnormality in the foetus. so no chances of release of egg and fertilization. 17. Two principle procedures adopted for such 2 Marks Questions technologies are: 7. CuT is a intrauterine device which releases (i) In vitro fertilization: The gametes are fused copper ions. Copper ions suppress the sperm in glass under conditions similar to the body motility and fertilizing capacity of sperms. It also increases the phagocytosis of sperms. It is also (ii) Embryo transfer: The developed embryo is a non-hormonal and non-steroidal with no side transferred to the body of a woman who can effects. carry pregnancy. 8. Contraceptive pills are made up of combination of 18. In Intra-Cytoplasmic Sperm Injection, the progestogen-estrogen or progestogen only. They nucleus of sperm is directly injected into the inhibit ovulation, inhibit implantation, and alter egg outside the female body and in Gamete quality of cervical mucus to retard entry of sperms. Intra Fallopian Transfer, egg and sperm are Non steroidal contraceptive oral pill is Saheli. transferred into the fallopian tube of the women, fertilization takes place inside the body. 9. Saheli is non-steroidal and non-hormonal contraceptive pill and has no or minimum side 19. Intra cytoplasmic sperm injection and zygote effects. It inhibits ovulation thereby inhibiting intra fallopian transfer. the motility and secretory activity of oviducts, it disables transport of sperms by impairment 20. GIFT: Gamete intra fallopian transfer. of cervix and make uterus unsuitable for ICSI: Intra Cytoplasmic Sperm Injection. implantation. 21. Refer answer no. 14. 22. ZIFT, GIFT, ICSI, IUI 10. Implants are surgically implanted under the skin and release progestogens alone or combination 3 Marks Questions with estrogen which acts as effective birth control method similar to pills. One can forget consuming 23. (a) RCH takes care of uncontrolled population pills but in implants, the hormones are released growth, sexually transmitted diseases, social continuously. Its advantage is that their effective evil like sex abuse and other sex related periods are much longer. crimes. 11. Reasons for increase in population are: (b) In amniocentesis, amniotic fluid is tested (i) Increase in health facilities, for chromosomal pattern of foetal cell to determine any abnormality in chromosomes. (ii) Better living conditions There is a statutory ban on it as most of the Steps taken by government to check population people use this test to determine sex of unborn child which leads to female foeticide. explosion are: (i) Motivate couples to use contraceptive to keep family small 72 Biology–12

24. Reproductive health includes total well being of 29. (a) An ideal contraceptive should be physical, emotional, behavioural and social aspects (i) User friendly and easily available of reproduction. The arguments which can justify the topic are: (ii) With no side effects, (i) The student's age is appropriate to learn (iii) Effective and reversible about the sexual changes in his/her body which helps him/her to avoid misconceptions, (iv) Should not interfere with sexual drive leads to mental and physical health. (b) Copper–T and Multiload 375 (ii) Lack of knowledge can lead to unwanted 30. Refer answer no. 8. pregnancies. 31. Surgical method for birth control are: Male: Vasectomy a part of vas deferens is (iii) This will also help student to prevent sexually transmitted diseases like AIDS and removed and ends are tied. gonorrhoea. Female: Tubectomy, a part of fallopian tube is (iv) It will create awareness about repro-ductive removed and the cut ends are tied. health and give way to curb problems of infertility, population explosion, maternal Advantage: and infant mortality etc. Surgical method is a fool proof and effective birth 25. (a) Provide right information to the young so as to control method. discourage children from believing in myths and misconception about sex related aspects Disadvantage: is about providing information of: This method is irreversible, so this method is (i) Safe hygienic practices about reproductive advised only to such couples who already have organs and related changes during children and do not want to increase their adolescence. number. (ii) STDs/AIDS, Available birth control 32. When an egg fuses with two X-chromosomes it will options, care of pregnant mothers, post fertilize with sperm containing Y-chromosome, natal care and importance of breast the foetus will carry XXY chromosomes which feeding is a genetic abnormality. The foetus will have Klinfelter’s syndrome. Such individuals are (iii) Equal opportunities for male and female sterile and will possess feminine characters child, sex abuse and sex related crimes including gynaecomastia. (iv) Problems arising due to uncontrolled 33. (a) Female partner is blamed due to social mind population growth set of male dominated society in our country. Sexual inequality exists because there is a (b) Reproductively healthy society indicators are: lack of awareness in this issue. (i) Has more number of assisted deliveries (b) As a biology student I can create awareness and better post natal care, there is that abnormality can occur in both male or decrease in IMR (Infant Mortality Rate) female or both due to which there is infertility and MMR (Maternal Mortality Rate) and can educate them with scientific (ii) Families are small knowledge so their myths are busted and (iii) More medical facilities are available for they do not believe in any superstitions. sex related problems and STDs (iv) Social, physical, emotional and behavioral Mutual respect towards both the partners can equality among different sexes. (any Two) be generated and I can help them to find the 26. Refer answer no. 7. medical remedy by experts instead leading 27. Lactational amenorrhea refers to absence of them to quacks. menstruation. This method is based on the fact that the ovulation and the menstrual cycle do (c) Physical abnormality in reproductive system, not occur during the period of intense lactation congenital, immunological or psychological following parturition. This method is effective effects are also responsible only upto a maximum period of six months. As devices or medicines are used here, the side (d) If male partner is having problem, the couple effects are negligible. can adopt any one of the following techniques 28. To stop female foeticide, Government of India has put statutory ban on amniocentesis. It is named (i) Intra Cytoplasmic Sperm Injection (ICSI) so because foetal cells from amniotic fluid is taken and cultured to check for any abnormality in the (ii) Artificial Insemination (AI) foetus. (iii) Intra Uterine Insemination (IUI) 34. (a) CuT, Cu7, Multiload 375, (b) Refer answer no. 7 35. (a) Refer answer no. 8. (b) These pills are taken daily for 21 days. During menstruation the pills are not taken. Reproductive Health  73

36. (i) ZIFT (Zygote intra fallopian transfer)– 5 Marks Questions Zygote or early embryo upto 8 blastomeres is transferred to fallopian tube. 38. ARTs enable the infertile couple to fulfill their desire of a child by employing different available (ii) GIFT (Gamete Intra fallopian transfer)–egg scientific methods such as ZIFT, GIFT, IVF, IUT, of a donor female and sperm of donor male ICSI, AI and in vivo fertilization. ZIFT involves in transferred to the fallopian tube of female transfer of embryo upto 8 blastomeres into the who cannot produce it but have suitable body fallopian tube. for fertilization and further development. GIFT involves transfer of ovum collected from a (iii) IUT (Intra Uterine Transfer)–Embryo with donor female into the fallopian tube of another more than 8 blastomeres is transferred to female which cannot produce ovum but has an uterus of a female. ability to fertilize and develop the embryo. Where as IUT involves transfer of embryo of more than 37. Yes, I do agree with the advice. The first milk 8 blastomeres into the uterus. called colostrums contains antibody, IgA which provides immunity and also contains nutrients. Assertion & Reason Type Questions For question numbers 1-12: Two statements are 7. Assertion (A): All sexually transmitted diseases given one labelled Assertion (A) and the other labelled are completely curable if it is detected and treated Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. properly in primary stage. (a) Both Assertion and Reason are true and Reason Reason (R): HIV infection is completely curable is the correct explanation of Assertion. with drugs like Zidovudine, Didanosine and (b) Both Assertion and Reason are true but Reason Azidothymidine. is NOT the correct explanation of Assertion. 8. Assertion (A): Now-a-days amniocentesis is (c) Assertion is true but Reason is false. banned. (d) Assertion is false and Reason is also false. 1. Assertion (A): Sponge and Delfin are chemical Reason (R): Amniocentesis gives the information of any abnormality in the fetus and many other methods of contraception. Reason (R): Diaphragms and cervical caps are complications regarding pregnancy can be disposable barrier method of contraception. detected. 2. Assertion (A): To achieve zero population 9. Assertion (A): In GIFT, fertilisation takes place growth rate, the replacement level should be in vivo. slightly higher than 2. Reason (R): Replacement level means the number Reason (R): The results of GIFT are less better of children that can replace parent equally. than in vitro fertilisation. 3. Assertion (A): Rhythm contraceptive method can be beneficial to the couple facing fertility 10. Assertion (A): Generally, a woman does not problem. conceive during the lactation period. Reason (R): Rhythm method is based on the ICSI technique. Reason (R): The hormone ‘prolactin’ initiates 4. Assertion (A): A medical termination of and maintains lactation in a postpartum woman. pregnancy is legally allowed upto the 28th week of pregnancy. 11. Assertion (A): Through Reproductive and Child Reason (R): MTP is done if family physician or Health (RCH) programmes in India, we could gynaecologist consider the need for abortion. 5. Assertion (A): PCR, ELISA, DNA hybridisation bring down the population growth rate. are confirmatory tests for sexually transmitted diseases. Reason (R): A rapid increase in MMR and IMR Reason (R): Incidence of STDs are very high in were the reasons, along other reasons for this. persons above the age of 30. 6. Assertion (A): Oral contraceptive pills check [CBSE 2022] ovulation. Reason (R): Oral pills always contains 12. Assertion (A): Sterilisation methods are combination of progesterone and estrogen. generally advised for male/female partner as a terminal method to prevent any more pregnancies. Reason (R): These techniques are less effective and have high reversibility. [CBSE 2022] 1. (c) Answers 5. (c) 6. (c) 10. (b) 11. (b) 2. (a) 3. (d) 4. (b) 7. (d) 8. (b) 9. (c) 12. (c) 74 Biology–12

Case Based Questions 1. Over population causes number of family (b) Cu ions make cervix hostile to the sperms. problems. Strategies like birth control methods help to control population explosion. Natural (c) Cu ions suppress sperms motility. methods of birth control do not involve (d) Cu ions inhibit ovulation. medications or devices to prevent pregnancy (ii) Which of the following IUDs makes uterus unsuitable for implantation? but rather rely on behavioural practices and/or making observations about menstrual cycle. (a) LNG-20 (b) Multiload 375 (i) Which method helps in contraception by (c) Cu7 (d) Lippes loop temporary absence of sex? (iii) Identify the correct statement for IUDs. (a) Coitus interruptus (a) They slowly release synthetic progesterone in the body. (b) Withdrawal method (b) They increase phagocytosis of sperms (c) Rhythm method within the uterus. (d) Lactational amenorrhea method (c) They block entry of sperms through the (ii) Assertion: The effectiveness of coitus cervix. interruptus method is limited. Reason: Some sperms may pass into vagina (d) Both (b) and (c). before ejaculation. (iv) Select the correct matched pair. (a) Both assertion and reason are true and reason is the correct explanation of (a) Hormone releasing IUD – LNG-20 assertion. (b) Non-medicated IUD – Progestasert (b) Both assertion and reason are true but (c) Copper releasing IUD – Lippes loop reason is not the correct explanation of (d) None of these. assertion. (v) Assertion: IUDs can cause excess menstrual bleeding and pain. (c) Assertion is true but reason is false. Reason: IUDs can perforate uterus. (d) Both assertion and reason are false. (a) Both assertion and reason are true and (iii) Why is lactational amenorrhea effective for reason is the correct explanation of about 4-5 months after parturition? assertion. (a) Ovulation occurs on about the 14th day of menstruation. (b) Both assertion and reason are true but (b) Ovulation does not occur during intense reason is not the correct explanation of lactation. assertion. (c) This method inhibits mobility of sperms. (c) Assertion is true but reason is false. (d) Both (b) and (c). (d) Both assertion and reason are false. (iv) Which fact is not the basis of periodic absence 3. A young couple married for 5 years is unable method of birth control? to bear a child inspite of not practicing any (a) Ovum remains alive for about 1-2 days. birth control method. Upon consultation, doctor (b) Ovulation occurs on about 14th day of advised them an assisted reproductive technology menstruation. involving transfer of gametes into oviducts. (c) Sperms survive for about 3 days. (i) Identify the technique adopted by the couple. (d) Alteration in uterine endometrium. (a) ZIFT (b) IUI (v) On which days of menstrual cycle should coitus be avoided to prevent fertilisation? (c) GIFT (d) ICSI (a) 10-17 (b) 6-13 (ii) What is the pre-requisite of this technique? (c) 1-5 (d) 15-28 (a) Gamete formation should be normal. 2. Intrauterine devices are most widely accepted (b) Fallopian tubes should be normal. methods of contraception. These are used by (c) Female should have thick endometrial lining. females and are inserted by doctor or nurses in the uterus through vagina. However, these (d) Male should be able to copulate the female. devices are not recommended for those eventually intend to conceive. (iii) Assertion: GIFT is an in-vitro fertilisation technique. (i) How does CuT prevent conception? Reason: In GIFT, gametes are fertilised (a) Cu ions make uterus unsuitable for outside the female body. implantation. Reproductive Health  75

(a) Both assertion and reason are true and (iv) Assertion: Amniocentesis is legally banned reason is the correct explanation of for sex determination. assertion. Reason: Amniocentesis was being misused for aborting normal female fetus. (b) Both assertion and reason are true but reason is not the correct explanation of (a) Both assertion and reason are true and reason is the correct explanation of assertion. assertion. (c) Assertion is true but reason is false. (b) Both assertion and reason are true but (d) Both assertion and reason are false. reason is not the correct explanation of (iv) The procedure advised to couple involves the assertion. transfer of (c) Assertion is true but reason is false. (a) fertilised ovum. (d) Both assertion and reason are false. (b) embryo with 8 blastomeres. (v) Which of these is a non-invasive technique of (c) sperms and unfertilised ovum. detecting fetal disorder? (d) embryo with 16 blastomeres. (a) Fetoscopy (v) What is the success rate of this procedure? (b) Chorionic villi sampling (a) 30-50% (b) < 20% (c) Amniocentesis (c) 80-85% (d) 27-30% (d) Ultrasound imaging 4. A technique known as amniocentesis is used to 5. Medical termination of pregnancy is termination determine fetal abnormalities. This test is based of pregnancy before the fetus becomes visible. on the chromosomal pattern in amniotic fluid. To reduce the incidence of illegal abortion However, this technique is legally banned now. and consequent maternal mortality. MTP X Amendment Act, 2017 was enacted by the government of India. About 40-50 million MTPs Y are done in a year all over the world. Z Fetus (i) Abortion can be safely done for about .......... weeks of pregnancy. Cells shed by (a) 4 (b) 12 growing fetus (c) 8-10 (d) 15-18 Syringe with needle withdraws (ii) How is MTP helpful in decreasing human a small amount of population? fluid and cells (a) By aborting normal female fetus (b) By increasing maternal mortality rate (c) By getting rid of unwanted pregnancies (d) None of these (i) Identify X and Y in the above given figure. (iii) Select the incorrect statement for MTP. (a) Second trimester abortions are more risky X Y than first trimester. (a) Amnion Chorion (b) It is being misused to abort normal female fetus. (b) Uterine wall Placenta (c) It helps to get rid of unwanted pregnancies. (c) Placenta Uterine wall (d) Child detected with congenital heart (d) Uterine wall Amnion disease cannot be aborted. (ii) What is the function of Z? (iv) MTP was legalised by Government of India (a) Z is an amniotic fluid which prevents in dessication of an embryo. (a) 1971 (b) 1982 (b) Z is yolk sac which functions as site of early blood cell formation. (c) 1973 (d) 1991 (c) Z is amnion which takes part in placenta (v) Assertion: MTPs are safe during trimester of pregnancy. formation. Reason: After first trimester, fetus become (d) None of these. intimately associated with the maternal (iii) Which of the following diseases can not be tissues. diagnosed by amniocentesis? (a) Both assertion and reason are true and (a) Down’s syndrome (b) Sickle cell disease reason is the correct explanation of (c) Jaundice (d) Cystic fibrosis assertion. 76 Biology–12

(b) Both assertion and reason are true but was advised to opt for assisted reproductive reason is not the correct explanation of technology (ART). assertion. (i) Which ART could have been useful for this (c) Assertion is true but reason is false. couple? (d) Both assertion and reason are false. (a) ZIFT (b) IUI 6. Oral administration of small doses of hormones is (c) AI (d) GIFT contraceptive method used by the females. They (ii) In which of the following infertility issues are used in the form of tablet and hence called could this technique be used? the pills. The oral pills are two types: mini pills (a) Anovulation (b) Oligospermia and combined pills. (c) Low fructose content in seminal fluid (i) Mini pills contain (d) All of these (a) estrogen only (b) progesterone only (iii) Which among the following techniques is (c) combination of progesterone-estrogen useful to conceive when there is very low (d) inhibin sperm count? (ii) How do hormonal pills prevent pregnancy? (a) GIFT (b) Test-tube baby (a) By phagocytosing the sperms (c) IUT (d) ICSI (b) By inhibiting ovulation (iv) Assertion: Artificial insemination (AI) is intra-uterine insemination. (c) By preventing sperms from entering the vagina Reason: In AI, sperms collected from donor (d) All of these. are introduced into the uterus. (iii) Pill containing non-steroidal preparation, (a) Both assertion and reason are true and centchroman is reason is the correct explanation of (a) Mala D (b) Mala N assertion. (c) i-Pill (d) Saheli (b) Both assertion and reason are true but (iv) Which among the following is incorrect for reason is not the correct explanation of oral contraceptives? assertion. (a) Oral pills alter the uterine endometrium and make it unsuitable for implantation. (c) Assertion is true but reason is false. (b) Oral pills have to be taken daily for 7 days (d) Both assertion and reason are false. starting within first five days of menstrual (v) Success rate of artificial insemination is cycle. (a) 20-40% (b) 60-70% (c) Oral pills increase the risk of intravascular (c) 40-50% (d) 5-7% clotting. 8. A women of 35 years age with a married life of eight years and having normal reproductive (d) Oral pills contain either progestin alone or combination of progesterone and cycles visits a doctor along with her husband for estrogen. consultation for infertility. They were not using (v) Assertion: Mala D, a combined contraceptive any contraceptive methods. They have no child. pill have to be taken daily without a break. The doctor advises them after a detailed physical R e a s o n : M a l a D c o n t a i n s s y n t h e t i c examination of both of them to undergo following progesterone and estrogen. investigations: (a) Both assertion and reason are true and — Seminal analysis of the husband reason is the correct explanation of — Follicular study of the wife assertion. — Blood test for Follicle Stimulating Hormone (b) Both assertion and reason are true but (FSH) estimation for both reason is not the correct explanation of With your basic knowledge of human embryology and the case given above, answer the following assertion. questions.(CBSE 2022) (c) Assertion is true but reason is false. (i) Seminal analysis of the husband was done for (d) Both assertion and reason are false. determining 7. A woman unable to conceive after many years of (I) Sperm morphology and sperm count regular unprotected coitus went to specialised (II) Quantity and pH of semen infertility clinic. On complete examination, (III) Rate of sperm release into the Vagina woman was found to be normal while male (a) (I) only (b) (I) and (II) partner was diagnosed with infertility. Male (c) (II) and (III) (d) (II) only partner is unable to copulate with female. Couple Reproductive Health  77

(ii) An ultrasound – guided follicular study was it shows high levels of L.H. and estrogen? done for the wife for determining the size and (a) Ovulatory phase (b) Menstrual phase physical appearance of the (c) Secretory phase (d) Follicular phase A ns. 1. (i) (c) (ii) (a) (a) Ovary (b) Oogonia (iii) (b) (iv) (d) (v) (a) (c) Antral follicles (d) Corpus Luteum 2. (i) (c) (ii) (a) (iii) (b) (iv) (a) (iii) The blood test report of the wife showed low (v) (b) FSH value, which is indicative of 3. (i) (c) (ii) (b) (iii) (d) (iv) (c) (a) low rate of formation of ovarian follicles. (v) (d) 4. (i) (b) (ii) (a) (b) high rate of formation of ovarian follicles. (iii) (c) (iv) (a) (v) (d) (c) low rate of maturation of ovarian follicles. 5. (i) (b) (ii) (c) (iii) (d) (iv) (a) (d) high rate of maturation of ovarian follicles. (v) (a) 6. (i) (b) (ii) (b) (iv) In the above case if the husband is found to (iii) (d) (iv) (b) have sperm count of less than 20 million/mL (v) (b) 7. (i) (c) (ii) (b) and the wife is diagnosed with blockage in the (iii) (d) (iv) (a) (v) (a) oviduct, the couple would be advised for: 8. (i) (b) (ii) (c) (iii) (c) (iv) (b) (i) ZIFT (ii) AI (v) (d) (vi) (a) (iii) IVF (iv) ICSI qqq (a) (i) and (iii) (b) (ii) and (iii) (c) (iii) and (iv) (d) (i) and (iv) (v) The high level of which gonadotropin/ovarian hormone in the blood sample of the wife taken on day 20 of her reproductive (menstrual) cycle would indicate the letual phase of the ovarian cycle? (a) FSH (b) LH (c) Estrogens (d) Progesterone (vi) In which phase of the menstrual cycle is the blood sample of a women taken if, on analysis, 78 Biology–12

4 Principles of Inheritance and Variation Topics Covered 4.1 Mendel’s Laws of Inheritance 4.2 Inheritance of one Gene: Monohybrid Cross 4 .3 Inheritance of two Genes: Dihybrid Cross 4 .4 Inheritance of more than two genes: Polygenic Inheritance 4 .5 Chromosomal Theory of Inheritance 4.6 Linkage and Recombination 4 .7 Sex Determination 4.8 Genetic Disorders C hapter map PRINCIPLES OF INHERITANCE AND VARIATION Genetic Disorders Inheritance Sex Determination Mendelian Polygenic Haplo diploidy Female Male disorders Inheritance E.g. Honey bees heterogamety heterogamety Thalassemia • Chromosomes Chromosomal • Genes ZO Female ZW Female ZZ Male Eg: Moths ZZ Male Eg: Birds, disorders Mendelian Butterflies, Domestic Down’s syndrome, Inheritance Reptiles, some • Incomplete chickens Fishes Klinefelter’s dominance syndrome, Turner’s • Co-dominance XX Female XO XX Female XY • Pleiotropy Male Eg: Bugs, Male Eg: Man (Barr bodies– X syndrome cockroaches, Simple dominance Multiple alleles Grasshoppers inactivation), Drosophila Eg: ABO blood Sex linked (Genic balance mechanism) Co-dominance X linked Eg: Haemophilia, grouping in human being Colour blindness Topic 1. Mendel’s Laws of Inheritance • Gregor Mendel conducted experiments on garden Plant was self pollinated, so he got many true breeding varieties. pea and gave the laws of inheritance. • His laws are the basis of modern genetics so he is It was easy to do cross pollination among plants. He applied mathematical and statistical tools to also called as the father of genetics. his samples for giving conclusions. • Genetics is the study of heredity and variation of His sampling size was also larger which gave more the characteristics passed from parents to their credibility to the data he collected. offsprings. He studied seven true breeding contrasting • Mendel got success due to the following reasons: characters. He chose a plant with shorter life cycle so he was One character was used at a time for obtaining able to study many generations. results. 79

Contrasting Traits Studied by Mendel in Pea S. No. Characters Contrasting Traits 1. Stem height Tall/dwarf 2. Flower colour Violet/white 3. Flower position Axial/terminal 4. Pod shape Inflated/constricted 5. Pod colour Green/yellow 6. Seed shape Round/wrinkled 7. Seed colour Yellow/green • Mendel’s work was not accepted initially as he physical proof of factors which controlled the did not publish his work in a journal which had characters. wide circulation, his explanations of factors and use of mathematical laws were not accepted • In 1900, three scientists, De Vries, Correns and by his counterparts. He could not provide any Von Tschermak rediscovered Mendel’s work independently. Topic 2. Inheritance of one Gene: Monohybrid Cross • Mendel crossed true breeding tall and dwarf pea produced dwarf plants in the coming generations. plants. The seeds produced by this cross were the tfihresstefislieaeldpsr,ohgeenoybsoerrFve1 dgetnheartaatilol np.lWanhtesnwheeregrteawll • He crossed tall plants of tFh2atg enera tion with and none were dwarf. dwarf plants and observed if the tall plant • aWthnahdteoninthFFe12rsgpewlanenerrtesadtwiwoenarrsefoismneeltfhopef otrhlaleitniooafftosefpd3r,:i1nh.geTsohwbeesrreeerwvtaealdsl is homozygous, all plants will be tall and if it is no blending of characters. When he self pollinated F2 generation plants, he observed that dwarf plants heterozygous, 50% of plants will be tall and 50% dwarf. He called such cross as test cross. Test cross is used to know the unknown genotype of an individual. • Similar results were obtained for flower colour in test cross as shown in the given figure. Homozygous Homozygous recessive recessive WW ww ww ? ww W W Ww Ww WW Ww Ww Ww W Ww Ww Dominant Phenotype w Result All flowers are violet (Genotype unknown) ww Interpretation Unknown flower is homozyous dominant ww 80 Biology–12 Half of the flowers are violet and half of the flowers are white Unknown flower is heterozygous

• He obtained similar results with other contrasting show any blending and that both the characters are characters. recovered ansotsusecheninatththeeFF21gsetnaegrea.tion though one of these is Parental Dwarf Punnett Square Tall • A diagram which is used to understand the production of gametes, and formation of zygotes of all possible genotypes of an offspring is called Punnett square. It was developed by British geneticist, Reginald C. Punnett. F1 generation Incomplete Dominance Selfing • While doing similar experiments with other plants Tall Tall as Mendel’s, it was observed that F1 generation did not resemble with either of the two parents. F2 generation • Example: In dog flower, the cross between true Tall Tall Tall Dwarf breeding red flower and true breeding white flower, pink flowers were obtained in F1 generation. The • On the basis of this experiment he concluded that: phenotypic ratio obtained in F2 generation was 1:2:1 There are two alternative forms (alleles) instead of 3:1 for the same factor (later called as gene). Thus factors are present in pairs. • Here a third phenotype is produced which is a For true breeding variety, the allelic pairs are combination of the phenotypes of both alleles. similar, i.e. homozygous. sGaemneotayspoefohfoFm1oizsyhgeotuesropzayrgeonut.s but phenotype is • The gene can become dominant or recessive due to Only one parental allele expresses itself in the mutation or modification. presence of another. There is no blending in characters when both • The modified allele could lead to the production of: alleles are present together. 50% of alleles segregate randomly in gametes. The normal/less efficient enzyme, in this case the gene is equivalent to unmodified allele. • He proposed two laws on the basis of above observations The non-functional enzyme or No enzyme at all, in both of these cases phenotype is affected and trait will only be dependent upon unmodified allele. P generation White (rr) Red (RR) Law of Dominance Gametes R r (i) Characters are controlled by discrete units F1 generation called factors. All pink (Rr) (ii) Factors occur in pairs. Gametes RR Gametes (iii) In a dissimilar pair of factors one member r of the pair dominates (dominant) the other r (recessive). RR • The law of dominance is used to explain the Rr Rr expression of only one of the parental characters F2 generation in a monohybrid cross in the F1 and the expression oobf tbaoitnhedininththeeFF22..It also explains the ratio of 3:1 rr Law of Segregation Phenotypic ratio : red : pink : white • tThis law states that gametes receive only one 1: 2: 1 allele of the two factors randomly. The alleles do not Genotypic ratio : RR : Rr : rr 1 : 2 :1 Principles of Inheritance and Variation  81

Co-dominance IB i IB i B • Irnesethmibs lecabsoeththteheinpdairveindtusa(leqinuaFll1y generation will i i ii O in many cases). • This is also an example of multiple alleles wherein • Example is ABO blood grouping in humans. a character is controlled by more than two alleles. • ABO blood groups are controlled by gene I which has Pleiotropy three alleles, IA, IB and i. • Pleiotropism is defined as a phenomenon when • IA and IB produce slightly different form of sugar a single gene may produce more than one effect while i doesn’t produce any sugar. IA and IB both (the multiple effects of a gene) or control several are dominant over i. phenotypes depending on its position. • If IA and IB are present together they both express • This is due to the interrelationship among various equally. This is called co-dominance. metabolic pathways that may contribute towards different phenotypes. • Since there are three different alleles, six genotypes and four phenotypes are possible as shown in the • Example: In phenylketonuria, mutation of the gene given table. which codes for enzyme phenylalaninehydroxylase results in mental retardation, reduction in hair and Allele Allele Genotype Blood skin pigmentation. from from of types of Parent 1 Parent 2 offspring • In Drosophila, white eye mutation leads to offspring depigmentation in many other parts of the body, IA IA A giving it a pleiotropic effect. IA IB IA IA AB IA IA IB A • In transgenic organisms, the introduced gene can IB i IA i AB produce different effects depending on where the IB IA IA IB B gene has integrated. IB IB IB Topic 3. Inheritance of two Genes: Dihybrid Cross • Mendel selected pea plants with two different characters, seed shape and seed colour. He crossed plants having round and yellow seeds (dominant traits) with plants having wrinkled and green seeds (recessive traits). • The result obtained is shown in the following figure: Round yellow Wrinkled green RR YY rr yy RY ry Round yellow Rr Yy Selfing RY RY Gametes rY RRYY rY Gametes Ry RrYY RrYY Ry ry RRYy rrYY RRYy ry RrYy RrYy RrYy RrYy rrYy RRyy rrYy Rryy Rryy rryy Phenotypic ratio Round yellow : Round green : Wrinkled yellow : Wrinkled green 93 3 1 82 Biology–12

• The phenotypic ratio obtained is 9:3:3:1 for round yellow, round green, wrinkled yellow and wrinkled green. Law of Independent Assortment • Based on the above observation, Mendel proposed the Law of Independent Assortment which states that ‘when two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters’. Topic 4. Inheritance of more than two genes: Polygenic Inheritance • In 1883, Galton suggested that some characters such as plant height, yield of crops (size, shape and number of seeds and fruits per plant), P generation × intelligence in human beings, mental capabilities, skin colour in humans and milk yield in animals are heritable and show continuous aabbbcc AABBCC range of variation in a population. Such variation can be determined (Very light) (Very dark) by more than one gene, each with same but cumulative phenotypic effect. Such effect is called quantitative inheritance or multiple F1 generation × factor inheritance. The more is the number of dominant genes, the AaBbCc AaBbCc greater will be the expression of the character. F2 generation Sperm • Example: Skin colour in human beings is controlled by three genes, 1 11111111 ‘A’, ‘B’ and ‘C’. When very dark skin coloured individual is crossed 88888888 with very fair skin coloured individual, F1 generation obtained is intermediate in colour. In F2 generation, a range of skin colour 8 is obtained from very dark to very light. Few individuals fall- 1 into parental categories. The expression level of the phenotype is 8 dependent upon the number of contributive alleles and hence it is 1 more quantitative. If the F2 data is plotted graphically, a bell-shaped curve is obtained as given in the figure. 8 1 8 Eggs 1 8 1 8 1 8 1 8 1 6 15 20 15 6 1 64 64 64 64 64 64 64 A cross showing polygenic quantitative inheritance of human skin colour Topic 5. Chromosomal Theory of Inheritance • With advancement of technology, two biologists, Walter Sutton and Theodore Boveri noted that chromosomes behaviour was similar to that of factors explained by Mendel. • Later it was established that factors were the two alleles of a gene located on homologous chromosomes. Sutton united the knowledge of chromosomal segregation with Mendelian Principles and called it the Chromosomal Theory of Inheritance. Principles of Inheritance and Variation  83

Topic 6. Linkage and Recombination • Thomas Hunt Morgan et. al. verified the chromosomal theory of inheritance when they worked on Drosophila melanogaster, the fruit fly. It was also observed that some genes remain together as they are passed from parents to their offsprings. This association was termed as linkage. The parental combination was obtained in higher percentage than non-parental recombinations. • Few genes which lie close to each other are tightly linked whereas those which are located at a distance allow the formation of recombinants as shown in the given figure. Cross A Cross B Parental yw y+ w+ wm w+ m+ Wild type Wild type yw wm Yellow, white Yellow, miniature yw yw wm wm F1 generation y+ w+ Wild type Yellow, white w+ m+ Yellow, miniature Wild type Gametes Parental Recombinant Parental Recombinant type (98.7%) type (1.3%) type (62.8%) type (37.2%) y+ w+ y+ w w+ m+ w+ m Wild type white Wild type miniature y w+ wm w m+ yw yellow, white yellow White, miniature white y+ w+ F2 generation yw y+ w w+ m+ w+ Wild type yw wm wm yw white Wild type miniature yw y w+ wm w m+ yellow, white yw wm wm yellow White, miniature white Linkage Results of two dihybrid crosses conducted by Morgan. Cross 'A' shows crossing between gene y and w; Cross B shows crossing between genes w and m. Here dominant wild type alleles are represented with (+) sign in superscript. Note: The strength of linkage between y and w is higher than w and m. Topic 7. Sex determination • Sex of an individual is determined by the presence of special type of chromosomes called sex chromosomes. These chromosomes show their effect differently in different organisms. Chromosomes other than sex chromosomes are called autosomes. 84 Biology–12

• In insects, like grasshoppers, XO type of sex bee. They develop as drones parthogenetically determination is seen. Males have only one (without fertilization). X chromosome whereas females have two X chromosomes. 16 32 • In humans and some insects like Drosophila XX-XY Gametes 16 16 16 type of sex determination is present. Females have 32 16 two X chromosomes and males have two different types of sex chromosomes namely, X and Y. This • Diploid male can also develop if a heterozygous is an example of male heterogamety as two types female is crossed with male. This is shown in the of gametes are formed in male, one of X type and following cross. other of Y type. xz/xa × xm/0 • In birds, ZZ-ZW type of sex determination occurs. cross Females have two different type of chromosomes, Z and W. Males have two Z chromosomes. This is xz xa xm × an example of female heterogamety as the gametes xz/xm xa/xm formed in female are of two types, Z and W. No sex chromosome Sex Determination in Honey Bee Crossing Crossing • In honey comb, two sizes of brood cells are seen. with xm with xm The smaller are for worker bees and larger ones are for drones. Drones are males. After insemination, xz/xm xm/xm xz/xm xm/xm female queen bee lay eggs in these brood cells. In larger cells, unfertilized cells are laid by queen Diploid Diploid male male Topic 8. Genetic Disorders Pedigree Analysis • Analysis of traits for several generations is done in the form of a family tree in cases where controlled crosses cannot be performed. A number of disorders in human beings have been found to be associated with the inheritance of changed or altered genes or chromosomes. • Some symbols are used to represent the traits in pedigree chart. Male Female Sex unspecified Affected individuals Mating Mating between relatives (consanguineous mating) Parents above and children below (in order of birth-left to right) Parents with male child affected with disease 5 Five unaffected offspring Principles of Inheritance and Variation  85

Mendelian Disorders Alpha (a) Thalassaemia is caused due to deletion of 16p (a part of chromosome) chromosome having • Disorders which are determined by mutation in single two alleles HBA1 and HBA2 which causes decrease gene and follow the principle of inheritance given by in alpha-globulin. Excess of beta (b) chains form Mendel during its transmission to offsprings. unstable tetramers. Haemophilia Beta (b) thalassaemia is caused due to mutation of HBB gene on chromosome 11. The beta (b) chain • It is a sex linked recessive disease caused due to is not formed. The excessive alpha (a) chains bind one of the defected proteins responsible for blood to the cell membrane of RBC and damage them. clotting. The heterozygous female is a carrier, haemophilic sons are mostly affected. This is also Delta (d) thalassaemia is caused due to absence of called as royal disease because Queen Victoria was delta chains which is about 3% in all normal adult the carrier of this disease and many family members haemoglobin. were affected. Chromosomal Disorders Colour Blindness • Chromosomal disorders are caused due to absence • It is sex linked recessive trait in which a person or excess or abnormal arrangement of one or more cannot distinguish red and green colour. When both chromosomes. This happens as a result of an error X chromosomes in females (homozygous) and single during segregation of chromosomes/chromatids during X chromosome (hemizygous) in males carry recessive cell division. Any gain or loss of chromosome is called allele, the person is colour blind. aneuploidy. Failure of telophase during cell division results in increase in whole set of chromosomes in an Carrier woman Normal man organisms. This is called polyploidy. XY Parents X XC Down’s Syndrome • It is caused due to trisomy of 21st chromosome. Gametes X XC XY Ova Sperms Affected individual is short statured with small head, furrowed tongue and partially open mouth. Offsprings XY Palm is broad with characteristic palm crease. The X person is mentally retarded with under developed XC XX XY physique and psychomotor systems. Normal girl Normal boy Klinefelter’s Syndrome X XC XY • It is caused due to an extra X-chromosome. Carrier girl Colour blind boy Individuals with such abnormality have overall masculine development but with developed breast 1 Normal Girl : 1 Carrier girl called gynaecomastia. They are sterile. 1 Normal Boy : 1 Colour blind boy Turner’s Syndrome Thalassaemia • It is caused due to absence of One X-chromosome. • It is a genetic defect in which the globulin chains of These females are sterile because they have haemoglobin are less than the actual required. If one rudimentary ovaries. They also lack secondary chain synthesis is less, the other chain is present in sexual characters. excess which accumulates, precipitates and damages the RBC. There are two main types of Thalassaemia, alpha (α) Thalassaemia and beta (β) Thalassaemia. EXERCISE I. Multiple Choice Questions 2. Conditions of a karyotype 2n ± 1 and 2n ± 2 are called: 1. All genes located on the same chromosome: (a) Form different groups depending upon their (a) Aneuploidy (b) Polyploidy relative distance (c) Allopolyploidy (d) Monosomy (b) Form one linkage group 3. Distance between the genes and percentage of (c) Will not from any linkage groups recombination shows: (d) Form interactive groups that affect the (a) a direct relationship phenotype (b) an inverse relationship (c) a parallel relationship (d) no relationship 86 Biology–12

4. If a genetic disease is transferred from a (c) all males phenotypically normal but carrier female to only some of the male progeny, the disease is: (d) all females (a) Autosomal dominant 14. The inheritance pattern of a gene over generations among humans is studied by the pedigree (b) Autosomal recessive analysis. Character studied in the pedigree (c) Sex-linked dominant analysis is equivalent to: (d) Sex-linked recessive (a) quantitative trait (b) Mendelian trait 5. In sickle cell anaemia glutamic acid is replaced by (c) polygenic trait (d) maternal trait valine. Which one of the following triplets codes for valine? 15. It is said that Mendel proposed that the factor controlling any character is discrete and (a) GGG (b) AAG independent. His proposition was based on the: (c) GAA (d) GUG 6. Person having genotype IA IB would show the (a) results of F3 generation of a cross. blood group as AB. This is because of: (b) observations that the offspring of a cross made between the plants having two contrasting (a) Pleiotropy (b) Co-dominance characters shows only one character without (c) Segregation any blending. (d) Incomplete dominance (c) self pollination of F1 offsprings (d) cross pollination of F1 generation with 7. ZZ / ZW type of sex determination is seen in: (a) Platypus (b) Snails recessive parent. (c) Cockroach (d) Peacock 16. The cause of Down’s Syndrome in humans is: 8. A cross between two tall plants resulted in (a) Extra copy of an autosome offspring having few dwarf plants. What would be the genotypes of both the parents? (b) Extra copy of a sex chromosome (a) TT and Tt (b) Tt and Tt (c) Absence of an autosome (c) TT and TT (d) Tt and tt (d) Absence of a sex chromosome [CBSE 2022] 9. In a dihybrid cross, if you get 9:3:3:1 ratio it 17. Which of the following features show the denotes that: mechanism of sex determination in honey-bee? (a) The alleles of two genes are interacting with (i) An offspring formed from the union of a sperm and egg develops as a male. each other (ii) Males have half the number of chromosomes (b) It is a multigenic inheritance than that of female. (c) It is a case of multiple allelism (iii) T h e f e m a l e s a r e d i p l o i d h a v i n g 3 2 (d) The alleles of two genes are segregating chromosomes. independently. (iv) Males have father and can produce sons. 10. Which of the following will not result in variations among siblings? (a) (i) and (ii) (b) (ii) and (iii) (a) Independent assortment of genes (c) (i) and (iv) (d) (ii) and (iv) (b) Crossing over (c) Linkage [CBSE 2022] (d) Mutation 18. Select the pair that is incorrect: 11. Mendel’s Law of independent assortment holds (a) Sickle-cell anemia : Autosome linked recessive trait good for genes situated on the: (b) Haemophilia : Autosome linked recessive trait (a) non-homologous chromosomes (c) Colour blindness : Sex linked recessive trait (b) omologous chromosomes (d) Thalassemia : Autosome linked recessive trait (c) extra nuclear genetic element [CBSE 2022] (d) same chromosome 19. An example of a human trait where a single gene 12. Occasionally, a single gene may express more can exhibit multiple phenotypic expression is– than one effect. The phenomenon is called: (a) Phenyl ketonuria (b) Cystic fibrosis (a) multiple allelism (b) mosaicism (c) Thalassemia (d) Haemophilia (c) pleiotropy (d) polygeny [CBSE 2022] 13. In a certain taxon of insects some have 17 chromosomes and the others have 18 chromosomes. 20. Life cycle of Drosophila melanogaster is completed in– The 17 and 18 chromosome-bearing organisms are: (a) 7 days (b) 14 days (a) males and females, respectively (c) 21 days (d) 28 days (b) females and males, respectively [CBSE 2022] Principles of Inheritance and Variation  87

21. How many types of gametes would develop by an 28. Colour-blindness is a sex linked recessive trait organism with genotype AaBBCcDD? in humans. A man with normal colour vision (a) 1 (b) 2 marries a women who is colourblind. What would (c) 3 (d) 4 [CBSE 2022] be the possible genotypes of the parents, the son 22. In Pisum sativum the flower colour may be Violet and the daughter of this couple? (V) or White (v). What proportion of the offsprings Mother Father Daughter Son in a cross of VV × vv would be expected to be violet? (a) XX XCY XCX XY (a) 25% (b) 50% (b) XCXC XCY XCXC XCY (c) 75% (d) 100% [CBSE 2022] (c) XCX XY XCX XY 23. Which one of the gene pair is expected to give a (d) XCXC XCX XCY ratio of 1 : 1 : 1 : 1 in the progeny of a Mendelian XY Dihybrid cross? [CBSE 2022] (a) AaBb × AaBb (b) AABB × AaBb 29. How many types of gametes can be produced in a diploid organism which is heterozygous for 4 loci? (c) AaBb × aabb (d) AABB × aabb (a) 4 (b) 8 [CBSE 2022] (c) 16 (d) 32 24. The progeny of a cross between two snap-dragon plants, heterozygous for flower colour, bearing [CBSE 2022] different coloured flower would be: 30. Given below a Karyotype obtained after analysis of foetal cells for probable genetic disorder. (a) 50% pink, 50% white (b) 25% red, 50% pink, 25% white (c) 50% red, 50% white (d) 75% red, 25% white [CBSE 2022] 1 2 345 25. Study the given pedigree of a family and select the trait that shows this pattern of inheritance: 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 X Y Based on the above Karyotype, the chromosomal disorder detected in unborn foetus and the (a) Autosomal recessive, Phenylketonuria consequent symptoms the child may suffer from (b) Sex-linked recessive, Colour-blindness are– (c) Autosomal dominant, Myotonic dystrophy (a) Down’s syndrome : Gynaecomastia, overall masculine development (d) Sex-linked dominant, Vitamin-D resistant rickets [CBSE 2022] (b) Down’s syndrome : Furrowed tongue, short stature 26. A child with blood group A has father with blood group B and mother with blood group AB. What (c) Klinefelter’s syndrome : Gynaecomastia, would be the possible genotypes of parents and Masculine development the child? Choose the correct option: (d) Klinefelter’s syndrome : Rudimentary ovaries, Father Mother Child short stature [CBSE 2022] (a) IAi IBi IAi (b) IAIB IAi IAIA II. Fill in the Blanks (c) IBi IAIB IAi 1. Identical means ______ . (d) IBIB IAIB IAIA 2. Genes which code for a pair/collection of [CBSE 2022] contrasting traits are known as ___ . 27. In a dihybrid Mendelian cross, garden pea plants 3. _____ conducted hydridisation experiments on heterozygous for violet flowers and round seeds garden peas. are crossed with homozygous white flowers and 4. Hybrids which contain alleles that express wrinkled seeds. The genotypic and phenotypic contrasting traits are called ____ ratio of F1 progeny would be 5. Characters are controlled by discrete units called (a) 9 : 3 : 3 : 1 (b) 1 : 2 : 2 : 1 _____ . (c) 1 : 1 : 1 : 1 (d) 3 : 1 [CBSE 2022] 6. In a pair of dissimilar factors one is _____ factor. 88 Biology–12

7. Chromosomes are called _____ . 4. What is a Mutagen? Name a physical factor that 8. Failure of segregation of chromatids during can be a Mutagen.  [Foreign 2016] cell division cycle results in the gain or loss of a 5. What is point mutation? Give one example. chromosome(s), called _____ . [Foreign 2016] 9. An analysis of traits is a several generations of 6. Name the event during cell division cycle that a family is called ____ analysis. results in the gain or loss of chromosome. 10. The mechanism of _____ ______ has always been [Delhi 2011] a puzzle before the geneticists. 7. Give an example of a human disorder that is caused due to a single gene mutation. III. True or False 1. A true breeding line is one that, having undergone [Delhi 2016] continuous self-pollination, shows the stable 8. A geneticist interested in studying variations and trait inheritance and expression for several patterns of inheritance in living beings prefers to generation. choose organisms for experiments with shorter life cycle. Provide a reason. [Delhi 2015] 2. Mendel selected 12 true-breeding pea plant varieties, as pairs which are similar except for 9. Mention any two contrasting traits with respect one character with contrasting traits. to seeds in pea plant that were studied by Mendel.  [All India 2014] 3. Sutton conducted the hybridisation experiments on garden pea. 10. Name the contrasting pod-related traits studied by Mendel in pea plant experiment. 4. An analysis of traits is several generations of a family is called Punnett analysis. [All India 2011 C] 5. Characters are controlled by discrete units called 11. Mention two contrasting flower-related traits factors. studied by Mendel in his pea plant experiments.  [All India 2011 C] 6. Genes which code for a pair/collection of contrasting traits are known as alleles. 12. On what basis is the skin colour in humans considered polygenic? [All India 2015] 7. Mendel attributed the physical association or linkage of two genes and coined the terms linkage 13. How many kinds of phenotypes would you expect and recombination. cino-Fd2omgeinnearnacteio?n in a monohybrid cross exhibiting [Delhi 2014 C] 8. Haemophilia is a Mendelian disorder. 14. Name the respective pattern of inheritance where F1 phenotype IV. Match the items of Column I with those of (a) does not resemble either of the two parents Column II and is in between the two. Column I Column II (b) resembles only one of the two parent. (i) Mendalian (A) Sickle cell 15. How would you find the genotype of an organism anaemia disorder exhibiting a dominant phenotype trait? (B) Phenylketonuria (ii) Chromosomal [Delhi 2012 C] disorder (C) Down’s 16. Write the percentage of the pea plants that would syndrome (iii) Chromosomal btaellhFom1 hoeztyegroouzsygroeucesspsievaepinlanFt2sgaerneesrealtfieodn?when disorder [Delhi 2011 C] (D) Turner’s (iv) Mendel 17. Write the percentage of the pea plants that would syndrome be heterozygous tall pinlaFn2tsgaerneersaetlfieodn. when tall heterozygous F1 pea ( E) Laws of Heredity (v) Mendalian disorder [Delhi 2012 C] 1 Mark Questions 18. In a test cross progeny of pea plants, all were bearing violet flowers. Give the genotypes of the 1. A garden pea plant A produced inflated yellow parent pea plant. [All India 2012 C] pod, and another plant 'B' of the same species 19. Differentiate between Incomplete dominance and produced constricted green pods. Identify the co-dominance.  [All India 2011] dominant traits. [Delhi 2012] 20. Mention the type of allele that expresses itself 2. A garden pea plant produced axial white only in homozygous state in organism. flowers. Another plant of the same species [Foreign 2011] produced terminal violet flowers. Identify the 21. When a tall plant was self-pollinated, one-fourth dominant traits.  [All India 2012] of the progeny were dwarf. Give the genotype of 3. State a difference between a gene and an allele. the parent and dwarf progenies. [Delhi 2016] [All India 2008 C] Principles of Inheritance and Variation  89

22. Name the stage of cell division where segregation 36. The son of a haemophilic man may not get this of an independent pair of chromosome occurs. genetic disorder. Mention the reason.  [All India 2014] [Delhi 2010 C] 37. Write the cause of Down's syndrome in humans. 23. A garden pea plant produced axial white flowers.  [All India 2010 C] Another of the same species produced terminal 38. A haemophilic son was born to normal parents. violet flowers. Identify the dominant traits. Give the genotypes of the parents. [Delhi 2009 C]  [Delhi, All India 2012] 39. Name the type of cross that would help to find 24. In a dihybrid cross, when would the proportion of the genotype of a pea plant bearing violet flowers. parental gene combinations be much higher than  [All India 2017] non-parental types, as experimentally shown by Morgan and his group?  [All India 2012] 2 Mark Questions 25. A male honeybee has 16 chromosomes whereas 40. A plant of Antirrhinum majus with red flowers its female has 32 chromosomes. Give one reason. was crossed with another plant of the same  [All India 2016] gspeneceireastiwonithbowrehpitienkflfolwoweresr.s.TEhxepplalainnttsheofptahtteeFrn1 of inheritance with the help of a cross. 26. How many chromosomes do drones of honeybee  [All India 2008] possess? Name the type of cell division involved in the production of sperms by them. 41. Differentiate between male and female [All India 2015] heterogamety.  [Delhi 2015] 27. Identify and write the correct statement: 42. Explain mechanism of sex-determination in (a) Drosphila male has one X and one Y chromosome. birds.  [Delhi 2015] 43. Write the types of sex-determination mechanisms (b) Drosophila male has two X chromosomes. the following crosses show. Give an example of each type. [All India 2014] 28. Identify and write the correct statement: (a) Female XX with male XO (b) Female ZW with male ZZ.  [Delhi 2014] (a) In grasshopper males two sex chromosomes are X and Y types. 44. Explain why it is scientifically incorrect to blame the mother for bearing female child. (b) In grasshopper males there exist XO type of sex-determinants.  [All India 2014] [Delhi 2013 C] 45. The male fruit fly and female fowl are 29. Identify the correct statement: heterogametic while the female fruit fly and the (a) Female of many birds has a pair of dissimilar ZW chromosomes, while the males possess a male fowl are homogametic. Why are they called so?  [Delhi 2008] pair of similar ZZ chromosomes. 46. A woman with blood group ‘O’ married a man (b) Female of many birds has a pair of similar ZZ with AB group. Show the possible blood group chromosomes, while the males possess a pair of dissimilar ZW chromosomes. of the progeny. List the alleles involved in this inheritance. [All India 2008] [All India 2014 C] 47. When does a geneticist need to carry a test cross? 30. State the chromosomal defect in individuals with How is it carried? [Foreign 2015 C] Turner's syndrome.  [Delhi 2015 C] OR 31. Write the chromosomal defect in individuals affected with Klinefelter's syndrome. How does a test cross help to determine the genotype of an individual? [Foreign 2016] [Delhi 2015 C] 48. Give an example of a gene responsible for 32. Why do normal red blood cell become elongated multiple phenotypic expressions. What are such sickle shaped structures in a person suffering genes called? State the cause that is responsible for such an effect. [Foreign 2015 C] from sickle cell anaemia?  [Foreign 2014] 49. Why did T.H. Morgan select Drosophila 33. Name one autosomal dominant and one autosomal melanogaster to study sex-linked genes for his recessive Mendelian disorder in human. lab experiments?  [Foreign 2015 C] [Delhi 2010] 50. How does the gene 'I' control ABO blood groups 34. Write the genotype of (a) an individual who is in humans? Write the effect the gene has on the carrier of sickle cell anaemia gene but apparently unaffected, and (b) an individual affected with structure of red blood cells. [Delhi 2014] the disease. [All India 2010] 51. In snapdragon, a cross between true-breeding red flowered (RR) plants and true-breeding white 35. A human being suffering from Down's syndrome flowered (rr) plants showed a progeny of plants shows trisomy of 21st chromosome. Mention the with all pink flowers. cause of the chromosomal abnormality. (a) The appearance of pink flowers is not known [All India 2010] as blending. Why? 90 Biology–12

(b) What is this phenomenon known as? Look at the above diagram and answer the  [All India 2014] following questions. 52. Explain pleiotropy with the help of an example. (a) Write the genotypes of A, B, C, D  [Foreign 2014] (b) Write the phenotypes of A, B, C, D 53. A cross was carried out between two pea plants (c) Write phenotypic ratio of progeny. showing the contrasting traits of height of the (d) Write genotypic ratio of progeny. plants. The result of the cross showed 50% [All India 2009 C] parental characters. 62. A man with blood group A married a woman with B group. They have a son with AB blood group (a) Work out the cross with the help of a Punnett and a daughter with blood group O. Workout the square. cross and show the possibility of such inheritance. (b) Name the type of the cross carried out.  [Delhi 2008] [Delhi 2014] 63. Write the scientific name of the fruit fly. Why did Morgan prefer to work with fruit-files for his 55. In a typical monohybrid cross rthpehFe2npootpyupleatbiount rati o is wr itten as 3 : 1 fo experiments? State any three reasons. expressed as 1 : 2 : 1 for genotype. Explain with [All India 2014] the help of an example. [All India 2013] 64. L inkage and crossing over of genes are alternative 56. In a cross between two tall pea plants some of of each other. Justify with the help of an example. the offsprings produced were dwarf. Show with  [All India 2014] the help of Punnett square how this is possible. 65. Study the figures given below and answer the  [Delhi 2013] question. 54. A cross between a red flower bearing plant and Cross A a white flower bearing plant of Antirrhinum produced all plants having pink flowers. Work yw y+ w+ out a cross to explain how this is possible. [All India 2013] 57. Work out a cross to find the genotype of a tall pea yw plant. Name the type of cross.  [All India 2013] Yellow white Wild type 58. Tallness of pea plant is a dominant trait, while Cross B dwarfness is the alternate recessive trait. When a pure line tall is crossed with pure line wm w+ m+ dwarf, what fraction of tall plant in F2 shall be (Parental) heterozygous? Give reasons. [All India 2011 C] 59. When a tall pea plant was selfed, it produced wm one-fourth of its progeny as dwarf. Explain with White, miniature Wild type the help of a cross. [Delhi 2010] Identify in which of the given crosses, the 60. Identify a, b and c in the table given below: strength of linkage between the genes is higher. Pattern of Monohybrid Give reasons in support of your answer. inheritance F1expphreensostiyopnic 1. Co-dominance 66. Why is the possibility of a human female suffering a from haemophila rare? Explain. [Foreign 2014] 2. b The progeny resembled 67. only one of the parents. 3. Incomplete c This is the pedigree of a family tracing the dominance [All India 2009] movement of the gene for haemophilia. Explain 61. Tall plant × Tall plant: Phenotype the pattern of inheritance of the disease in the Tt Tt : Genotype family. [Delhi 2013 C] 68. A relevant portion of B chain of haemoglobin of a normal human is given below: tT Val His Leu Thr Pro Glu Glu Tt A 1234567 BD The codon for sixth amino acid is GAG. The C sixth codon GAG mutates to GAA as a result of Principles of Inheritance and Variation  91

mutation 'A' and into GUG as a result of mutation (b) Mention any one symptom of the diseases/ 'B'. Haemoglobin structure did not change as disorders named above. [Foreign 2015 C] a result of mutation 'A' whereas haemoglobin structure change because of mutation 'B' leading 76. Haemophilia is a sex-linked recessive disorder of to sickle shaped RBCs. Explain giving reasons humans. The pedigree chart given below shows how could mutation 'B' change the haemoglobin the inheritance of haemophilia in one family. structure and not mutation 'A'.[AIl India 2011] Study the pattern of inheritance and answer the questions given. 69. In a dihybrid cross white eyed, yellow bodied female Drosophila crossed with red eyed, 12 bgeronwernatbioodnie1d.3mpaelreceDnrtorseocpohmilbainparondtsucaenddin98F.72 percent progeny with parental type combinations. 3 45 6 78 9 This observation of Morgan deviated from gMiveinndgelrieaansFon2sp,hMenoortgyapni’csdoibhsyebrrviadtrioantiso.. Explain, 10 11 12 13 14 15 [Foreign 2011] (a) Give all the possible genotypes of the members 4, 5 and 6 in the pedigree chart. 3 Mark Questions (b) ‘A blood test shows that the individual 14 70. How would you find genotype of a tall pea plant is a carrier of haemophilia. The member bearing white flowers? Explain with the help of a cross. Name the type of cross you would use. numbered 15 has recently married the  [Delhi 2016] member numbered 14. What is the probability 71. Inheritance pattern of ABO blood groups in that their first child will be a haemophilic humans shows dominance, co-dominance and multiple allelism. Explain each concept with the male? [All India 2009] help of blood group genotypes.  [Delhi 2009] 77. Recently a girl baby has been reported to suffer from haemophilia. How is it possible? Explain OR with the help of a cross.  [All India 2009] How are dominance, codominance and incomplete OR dominance patterns of inheritance different from Why is haemophilia generally observed in human males? Explain the conditions under which a each other? [Delhi 2011] human female can be haemophilic. 72. (a) Explain the phenomena of multiple allelism and co-dominance taking ABO blood group as [All India 2009] an example. 78. Give an example of an autosomal recessive trait in humans. Explain its pattern of inheritance (b) What is the phenotype of the following: (i) IA i with the help of a cross. [Delhi 2016] (ii) i i 79. A couple with normal vision bears a colour blind [All India 2012] child. Work out a cross to show how is it possible 73. (a) State and explain the law of segregation and mention the sex of the affected child. as proposed by Mendel in a monohybrid cross. [Delhi 2016] (b) WinraitedithhyebrMidencrdoeslsia. nStFa2tePthheenolatwyptichartathioe proposed on the basis of this ratio. How is OR this law different from the law of segregation?  [Foreign 2015 C] A colour blind child is born to a normal couple. Work out a cross to show how it is possible. 74. (a) During a cross involving true breeding red Mention the sex of this child.  [Delhi 2014] flowered and true breeding white flowered 80. Given below is the representation of amino acid composition of the relevant translated portion of snapdragon pthlaenptsa,rethnetaFl 1trpariotsg,ewnyhidleidthneoyt show any of b-chain of haemoglobin, related to the shape of rmeeacphpaenaisrmeduisninFg2Ppurnongeettnsieqsu.aErex.plain the human red blood cells. Gene ---GAG--- ---CTC--- (b) Explain polygenic inheritance with the help of an example. [Foreign 2015] 75. (a) Name the kind of diseases/disorders that are mRNA ---GAG--- likely to occur in humans if (i) Mutation in the gene that codes for an Val His Leu Thr Pro Glu Glu enzyme phenyl alanine hydrolase occurs. 1 2 3 45 67 (ii) There is an extra copy of chromosome 21. HbA peptide (iii) The karyotype is XXY. 92 Biology–12

(a) Is this representation indicating a normal population studies are made\". Explain with the human or a sufferer from certain related help of an example in humans.  [Delhi 2012 C] genetic disease? Give reason in support of 88. Mendel published his work on inheritance of characters in 1865, but it remained unrecognised your answer. (b) What difference would be noticed in the till 1900. Give three reasons for the delay in phenotype of the normal and the sufferer accepting his work.  [Delhi 2014] related to this gene? 89. In pea plant let, symbol Y represent dominant (c) Who are likely to suffer more from the defect yellow; symbol y, the recessive green; symbol R, related to the gene represented – the males, the round seed shape and symbol r, the wrinkle the females or both males and females seed shape. A typical Mendelian dihybrid equally? And why?  [Delhi 2012] cross was carried out in pea plants. Write the 81. Which chromosome carry the mutant genes genotypes of causing thalassaemia in humans? What are the (a) Homozygous dominant and recessive parents problems caused by these mutant genes? (b) Gametes produced by both the parents [Delhi 2015 C] (c) F1 offspring 82. (a) Sickle cells anaemia in humans is a result of (d) Gametes produced by F1 offspring point mutation. Explain. [All India 2011 C] (b) Write the genotypes of both the parents who have produced a sickle celled anaemic 90. (a) Why are grasshopper and Drosophila said to show male heterogamety? Explain. offspring. [Delhi 2011] (b) Explain female heterogamety with the help 83. Study the given pedigree chart and answer the of an example.  [All India 2010] questions that follow: I 91. Explain the sex determination mechanism in humans. How is it different in birds?  II [All India 2010] 92. If there is a history of haemophilia in the III family, the chances of male members becoming (a) Is the trait recessive or dominant? haemophilic are more than that of the female. (b) Is the trait sex-linked or autosomal? (a) Why is it so? (c) Give the genotypes of the parents in (b) Write the symptoms of the disease. generation I and of their third and fourth [All India 2015 C] child in generation II. [All India 2008] 93. A cross between a normal couple resulted in a son 84. During a monohybrid cross involving a tall who was haemophilic and a normal daughter. In pea plant with a dwarf pea plant, the offspring course of time, when the daughter was married populations were tall and dwarf in equal ratio. to a normal man, to their surprise, the grandson Work out a cross to show how it is possible. was also haemophilic. [All India 2015] (a) Represent this cross in the form of a pedigree 85. The F2 progeny of a monohybrid cross showed chart. Give the genotypes of the daughter and phenotypic and genotypic ratio as 1 : 2 : 1, unlike her husband. that of Mendel's monohybrid F2 ratio. With the help of a suitable example, work out a cross and (b) Write the conclusion you draw of the inheritance pattern of this disease. explain how it is possible.  [All India 2015] [Delhi 2014] 86. Human population shows variations in the blood groups. Explain the genetic basis for this 94. Why is pedigree analysis done in the study of human genetics? State the conclusions that can variation seen in the population. be drawn from it.  [All India 2014] [All India 2013 C] 95. Identify a, b, c, d, e and f in the table given below. 87. \"Multiple alleles can be found only when  [All India 2014] No. Syndrome Cause Characteristics of Sex male/female/ affected individuals both 1. Down's Trisomy of 21 'b' 'a' (i) (ii) 'd' 2. 'c' XXY 'f ' Overall masculine development 3. Turner's 45 with XO 'e' (i) (ii) Principles of Inheritance and Variation  93

96. Name a disorder, give the karyotype and write 107. Explain with the help of a suitable example the symptoms a human suffers from as a result the inheritance of a trait where two different of monosomy of the sex chromosome. dominant alleles of a trait express themselves [Foreign 2011] simultaneously in the progeny. Name this kind 97. Name a disorder, give the karyotype and write of inheritance pattern. [All India 2014] the symptoms a human suffer from as a result of 108. During the studies on genes in Drosophila that were sex-linked, T.H. Morgan tfoeudnfdroFm2 an additional X-chromosome.  [Foreign 2011] population phenotypic ratios devia 98. Name the genetic disorder caused by trisomy expected 9 : 3 : 3 : 1. Explain the conclusion he of 21st chromosome in humans. Write the arrived at. [Delhi 2010] diagnostic features of the disorder. 109. State the three principles of Mendel’s law of [Delhi 2011 C] inheritance. 99. Study the following pedigree chart of a family 110. (a) Explain the mechanism of sex-determination starting with mother with AB blood group and in humans. father with O blood group. (b) Differentiate between male heterogamety Generation and female heterogamety with the help of one I O AB example of each. [All India 2013] Generation 1 111. Why is haemophilia rare in human females? II O A A Mention a clinical symptom for the disease. Generation 2 3 III [All India 2014] (a) Mention the blood group as well as it genotype 112. Name a blood related autosomal Mendelian disorder. Why is it called Mendelian disorder? of the offspring numbered 1 in generation II. How is the disorder transmitted from parents to (b) Write the possible groups as well as their offsprings? [All India 2014 C] genotypes of the offsprings numbered 113. Why are human females rarely haemophilic? 2 and 3 generation III. [Delhi 2010 C] Explain. How do haemophilic patients suffer? 100. What is a test cross? How can it decipher the [All India 2013] heterozygosity of a plant? [All India 2016] 114. Why is it that the father never passes the gene 101. A teacher wants his/her students to find the for haemophilia to his sons? Explain. genotype of pea plants bearing purple coloured [All India 2012] flowers in their school garden. Name and explain 115. Name the genetic disorder caused by an extra the cross that will make it possible.[Delhi 2015] ‘X’ chromosome in a human male. State the 102. (a) Write the conclusions Mendel arrived diagnostic features of the individual suffering at on dominance of traits on the basis of from it. [Delhi 2011 C] monohybrid crosses that he carried out in pea 116. (a) Name the genetic disorder in a human female plants. having 44 + XO karyotype. Mention the (b) Explain why a recessive allele is unable to diagnostic features of the disorder. express itself in a heterozygous state. (b) Explain the cause of such chromosomal [Foreign 2014] disorder. [Delhi 2011 C] 103. Explain polygenic inheritance with the help of a 117. Morgan carried out several dihybrid crosses in suitable example. [Delhi 2014 C] Drosophila and found F2- ratios deviated very 104. In pea plants, the colour of the flower is either significantly from the expected Mendelian ratio. violet or white whereas human skin colour shows Explain his findings with the help of one example. many gradations. Explain giving reasons how it  [Delhi 2014 C] is possible. [Delhi 2013 C] 118. Study the given pedigree chart showing the 105. When tall pea plants were selfed, some of the pattern of blood group inheritance in a family. offspring were dwarf. Explain with the help of a AB Punnett square. [Delhi 2011 C] 106. (a) Tallness of pea plant is a dominant trait, X OA dwarfness is the alternate recessive trait. A AB Y A pure tall pea plant is crossed to a dwarf one. (a) Give the genotype of the following: Work out the cross to show what fraction of the (i) parents tall plants in F2 generation is heterozygous? (ii) the individual ‘X’ in second generation (b) State any one law of Mendel which can be (b) Stat the possible blood groups of the individual derived form this cross. [Delhi 2008 C] ‘Y’ in third generation. 94 Biology–12

(c) How does the inheritance of this blood group 129. (a) State the cause and symptoms of colour- explain co-dominance?  [All India 2010 C] blindness in humans. 119. Both Haemophilia and Thalassemia are blood (b) Statistical data has shown that 8% of the related disorders in humans. Write their causes human males are colour-blind whereas only and the difference between the two. Name the 0.4% of females are colour-blind. Explain category of genetic disorder they both come giving reasons how is it so? under. [All India 2017] 130. Differentiate between the following: 120. E xplain the mechanism of ‘sex determination’ in birds. How does it differ from that of human (a) Polygenic inheritance and pleiotrophy. beings? [CBSE 2018] (b) Dominance, co-dominance and incomplete dominance. [All India 2013 C] 5 Mark Questions 131. Given below is a table showing the genotypes 121. A particular garden pea plant produces only and the phenotypes of blood groups in the human violet flowers. population: (a) Is it homozygous dominant for the trait or S.No Genotype Phenotype heterozygous? 1 (W) A (b) How would you ensure its genotype? Explain with the help of the crosses.[All India 2009] 2 iBiO (Y) 3 IAIB (Z) 122. How do “Pleiotropy”, “incomplete dominance”, “co-dominance” and “polygenic inheritance” 4 (X) O deviate from the observation made by Mendel? (a) Identify the genotypes (W) and (X) and the Explain with the help of one example for each. phenotypes (Y) and (Z).  [Delhi 2015 C] (b) How is co-dominance different from incomplete 123. (a) State and explain the law of dominance dominance and dominance? as proposed by Mendel. (c) Name the pattern of inheritance exhibited (b) HiFn2oSwpnrwaogpoeudnlrdaygpsohhneonawonitndygpceoisn-docofommmiopnnlaeonthecyebdrionimdhiFnu1amannacnde by the phenotypes (Y) and (Z) in the table.  [All India 2008 C] blood group be different from Mendelian 132. (a) A garden pea plant bearing terminal, violet monohybrid F1 and F2 progeny? Explain. flowers, when crossed with another pea plant  [Foreign 2015 C] bearing axial, violet flowers, produced axial, 124. Human blood group is a good example of multiple violet flowers and axial, white flowers in the allelism and co-dominance. Justify. ratio of 3 : 1. [Foreign 2016] Work out the cross showing the genotypes of 125. (a) Explain a monohybrid cross taking seed coat the parent pea plants and their progeny. colour as a trait in Pisum sativum. Work out (b) Name and state the law that can be derived from this cross and not from a monohybrid the cross upto F2 generation. (b) State the laws of inheritance that can be cross. [Delhi 2012 C] derived from such a cross. 133. (a) State the law of independent assortment. (b) Using Punnett square demonstrate the law of (c) How is the phenotypic ratio of F2 generation independent assortment in a dihybrid cross different in a dihybrid cross? involving two heterozygous parents. 126. Describe the mechanism of pattern of inheritance of ABO blood groups in humans. [All India 2011] [All India 2010 C] 127. A homozygous tall pea plant with green seeds is 134. Why is thalassemia categorised as a Mendelian crossed with a dwarf pea plant with yellow seeds. disorder? Write the symptoms and explain the (i) What would be the phenotype and genotype cause of the disease. How does it differ from sickle of F1? cell anaemia? [All India 2013 C] (ii) WwiotrhktohueththeleppohfeanoPtuypnincertattisoqoufaFr2e.generation 135. (a) How does a chromosomal disorder differ from a Mendelian disorder? [All India 2008] (b) Name any two chromosomal aberration associated disorders. 128. What is the inheritance pattern observed in the size of starch grains and seed shape of (c) List the characteristics of the disorders Pisum sativum? Workout the monohybrid cross mentioned above that help in their diagnosis. showing the above traits. How does this pattern of inheritance deviate from that of Mendelian law [Delhi 2010] of dominance? 136. (a) What is polygenic inheritance? Explain with the help of a suitable example. Principles of Inheritance and Variation  95

(b) How are pleiotropic inheritance different from 145. Pea seeds with BB alleles have round seeds and polygenic pattern of inheritance? large starch grains, while seeds with bb alleles have wrinkled seeds with small starch grains.  [All India 2015] Work out the cross between these two parents. 137. (a) How are Mendelian inheritance, polygenic Explain the phenotypic ratio of the progeny with inheritance and pleitropy different from each respect to seed shape and the starch gain size of other? the progeny produced. [All India 2012 C] (b) Explain polygenic inheritance pattern with 146. (a) Explain multiple allelism in humans with the the help of a suitable example. help of a suitable example. [All India 2015] (b) M ultiple alleles can be found only when 138. (a) A couple with blood groups ‘A’ and ‘B’ population studies are made. Justify. respectively have a child with blood group ‘O’. [Delhi 2011 C] Work out a cross to show how it is possible 147. When a garden pea plant with violet flowers was and the probable blood groups that can be crossed with another plant with white flowers, expected in their other off-springs. 50% of the progeny bore violet flowers. (b) Explain the genetic basis of blood groups in (a) Work out the cross. human population. [All India 2015 C] (b) Name the type of cross and mention its 139. Work out a monohybrid cross upto F2 generation significance. between two pea plants and two Antirrhinum (c) How does the inheritance pattern of flower plants both having contrasting traits with respect colour in snapdragon differ from the above? to colour of flower. Comment on the pattern of [Delhi 2010 C] inheritance in the crosses carried above. 148. When a garden pea plant with green pods was [All India 2014 C] cross pollinated with another plant with yellow 140. (a) Differentiate between dominance and co- pods, 50% of the progeny bore green pods. dominance. (a) Work out the cross to illustrate this. (b) Explain co-dominance taking an example of human blood groups in the population. (b) How do you refer to this type of cross? Why is such a cross done? [All India 2010 C] [All India 2013] 149. Inheritance pattern of flower colour in garden 141. (a) List the three different allelic forms of gene ‘I’ pea plant and snapdragon differs. Why is this in humans. Explain the different phenotypic difference observed? Explain showing the crosses expressions, controlled by these three forms. upto F2 generation. [Delhi 2009] (b) A woman with blood group ‘A’ marries a man with blood group ‘O’. Discus the possibilities 150. You are given a red flower-bearing pea plant and a red flower bearing snapdragon plant. of the inheritance of the blood groups in the How would you find the genotypes of these two following starting with “yes” or “no” for each: plants with respect to the colour of the flower? (i) They produce children with blood group Explain with the help of crosses. Comment upon “A” only. the pattern of inheritance seen in these two (ii) They produce children some with “O” plants. [Delhi 2009] blood group and some with “A” blood 151. With the help of one example each provide group. [Delhi 2012] genetic explanation for the following observations: 142. (a) WtwoorpkuoruetbarecreodspseuapptolaFn2tsg,eonneerabteiaorninbgetvwioeleent (a) F1 – generation resembles one of two parents. (b) F1 – generation resembles both the parents. flowers and the other white flowers. [Delhi 2009 C] (b) (i) Name this type of cross. 152. A snapdragon plant homozygous for red flower (ii) State the different laws of Mendel that when crossed with a white flowered plant of can be derived from such a cross. the same species produced pink flowers in F1 [All India 2012 C] generation. 143. State and explain with the help of a cross, the (a) What is this phenotypic expression called? law of segregation as proposed by Mendel. (b) Work out the cross to show the F2 generation [All India 2012 C] when F1 was self-pollinated. 144. (a) Explain the genetic basis of ABO - blood groups in human population. Give the phenotypic and genotypic ratios of (b) How do ABO blood groups explain the F2 generation. phenomenon of dominance and co-dominance? (c) HgeonwotdyopyicouractoimospawrieththtehFos2ephoef nMoteynpdicelaiannd [All India 2012] monohybrid F2 ratios? [All India 2008] 96 Biology–12

153. Give a genetic explanation for the following cross. (b) How did Morgan show the deviation in When a tall pea plant with rounds seeds was inheritance pattern in Drosophila with crossed with a dwarf pea plant with wrinkled respect to this law? [All India 2013] seeds then all the individual of F1 populations 161. Using Punnett square show the bFr2edrepsualrtesntosf were tall with round seeds. However, selfing a dihybrid cross where the pure among F1 population led to a 9 : 3 : 3 : 1 have contrasting traits with reference to seed phenotypic ratio. [All India 2016] shape and seed colour in Pisum sativum. Give 154. (a) Dihybrid cross between two garden pea plant the phenotypic ratio. [Delhi 2013 C] one homozygous tall with round seeds and the 162. Using Punnett square show the results of F2 other dwarf with wrinkled seeds was carried. generation of dihybrid cross where the parents (i) Write the genotype and phenotype of the have contrasting traits with reference to pod F1 progeny obtained from this cross. (ii) Give the different types of gametes of the colour and seed shape in Pisum sativum. Give the phenotypic ratio. [All India 2013 C] F1 progeny. (iii) Write the phenotypes and its ratios of the 163. (a) A true breeding homozygous pea plant with green pods and axial flowers as dominant Fw2itghetnheeraetxipolnanobattaioinnepdroinvitdheids cross along by Mendel. characters, is crossed with a recessive homozygous pea plant with yellow pods and (b) HdiohwybwriedrecrtohsesoebssienrvDatrioosnosphofilFa2bpyroMgeonrgyaonf terminal flowers. Work out the cross upto F2 generation respectively. different from that of Mendel carried in pea (b) State the Mendelian principle which can plants? Explain giving reasons. be derived from such a cross and not from [Delhi 2015 C] monohybrid cross. [All India 2011] 155. A tall pea plant bearing violet flowers is 164. (a) A true breeding pea plant, homozygous for given with its unknown genotypes. Explain by inflated green pods is crossed with another working out the crosses how would you find the pea plant with constricted yellow pods (ffgg). correct genotypes with respect to the two traits What would be the phenotype and genotype mentioned only by “selfing” the given plants. of F1 and F2 generations? Give the phenotype ratio of F2 generation. [All India 2015 C] (b) State the generalisation proposed by 156. A pea plant producing yellow coloured and round seeds is given with unknown genotypes. Explain Mendel on the basis of the above mentioned how you would find the correct genotypes of the cross. [Delhi 2008] plants with respect to the two traits mentioned. 165. A true breeding pea plant homozygous for axial Work out the cross and name it. violet flowers is crossed with another pea plant [All India 2015 C] with terminal white flowers (aavv). 157. Workout a typical Mendelian dihybrid cross and (a) What would be the phenotype and genotype state the law that he derived from it. of F1 and F2 generations? [All India 2014] (b) Give the phenotype ratio of F2 generations. (c) List the Mendel’s generalisation that can be 158. A cross was carried out between a pea plant heterozygous for round and yellow seeds with a derived from the above cross. [Delhi 2008] pea plant having wrinkled and green seeds. 166. A tall pea plant with yellow seeds (heterozygous (a) Show the cross in a Punnett square. for both the traits) is crossed with a dwarf pea (b) Write the phenotype of the progeny of this plant with green seeds. Using a Punnett square cross. work out the cross to show the phenotypes and (c) What is this cross known as? State the purpose of conducting such a cross. the genotypes of F1 generation.[All India 2008] 167. Let ‘Y’ be the genotypic symbol for dominant  [Foreign 2014] yellow seed colour, symbol y for recessive green 159. (a) Work out cross between a tall pea plant seed colour, symbol ‘R’ for dominant round shape bearing violet flowers (heterozygous for both) of seed and symbol ‘r’ for recessive wrinkled seed with a dwarf pea plant having white flowers. shape in garden pea. Using these symbols explain Write the genotypes and phenotypes of the the Mendel’s law of independent assortment. progeny along with their ratios. [All India 2008 C] (b) Name such a cross and state its importance. 168. (a) Why are colour blindness and thalassemia [Delhi 2014 C] categorised as Mendelian disorders? Write 160. (a) Explain Mendel’s law of independent the symptoms of these diseases seen in people assortment by taking a suitable example. suffering from them. Principles of Inheritance and Variation  97

(b) About 8% of human male population suffers 174. Study the pedigree chart given below showing the from colour blindness whereas only about inheritance pattern of a human trait and answer the question that follow: 0.4% of human female population suffers from Aa Aa this disease. Write an explanation to show I how it is possible. [All India 2015] 169. Write the type and location of the gene causing Aa Aa Aa II aa thalassemia in humans. State the cause and symptoms of the disease. How is sickle cell anaemia different from this disease? III Aa aa Aa [Foreign 2014] (a) Give the genotype of the parents shown in 170. A child suffering from thalassemia is born to a generation I and of the son and daughter normal couple. But the mother is being blamed shown in generation II. by the family for delivering a sick baby. (b) Give the genotype of the daughters shown in (a) What is thalassemia? generation III. (b) How would you counsel the family not to blame the mother for delivering a child (c) Is the trait sex-linked or autosomal? Justify suffering from this disease? Explain. your answer. [Foreign 2008] (c) List the values your counselling can propagate 175. (a) A pea plant bearing axial flowers is crossed in the families. [Delhi 2013] with a pea plant bearing terminal flowers. 171. (a) State the cause and symptoms of Down’s The cross is carried out to find the genotype of syndrome. Name and explain the event the pea plant bearing axial flowers. Work out responsible for causing this syndrome. the cross to show the conclusions you arrive (b) Haemophilia and thalassemia are both at. examples of Mendelian disorder, but show (b) State the Mendel's law of inheritance that is difference in their inheritance pattern. universally acceptable.  [All India 2017] Explain how. [All India 2013 C] 176. (a) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues 172. Explain the causes, inheritance pattern and symptoms of any two Mendelian genetic disorders. worked with for their experiments. Explain  [All India 2010] the correlation between linkage and 173. (a) Explain Polygenic inheritance and Multiple recombination with respect to genes as allelism with the help of suitable examples. studied by them. (b) ”Phenylketonuria is a good example that (b) How did Sturtevant explain gene mapping explains Pleiotropy.” Justify.[All India 2017] while working with Morgan? [CBSE 2018] Answers I. Multiple Choice Questions 1 Mark Questions 1. (b) 2. (a) 3. (a) 4. (d) 5. (d) 1. Dominant traits are inflated green pods. 6. (b) 7. (d) 8. (b) 9. (d) 10. (c) 2. Dominant traits are axial violet flower. 11. (a) 12. (c) 13. (a) 14. (b) 15. (b) 16. (a) 17. (b) 18. (b) 19. (a) 20. (a) 3. Gene Allele 21. (d) 22. (d) 23. (c) 24. (b) 25. (a) 26. (c) 27. (c) 28. (d) 29. (c) 30. (c) It is a unit of inheri- It is a slightly a differ- tance that contains ent form of the same II. Fill in the Blanks information required gene for same char- to express a particular acter. 1. homozygous 2. alleles 3. mendel trait or an enzyme. 4. heterozygous 5. factors 6. dominant 7. coloured bodies 8. aneuploidy 9. pedigree 4. Any physical or chemical factor that causes 10. sex determination mutation is called mutagen. Physical factor that can be a mutagen is UV radiation or X- rays. III. True or False 5. Mutation due to change in a single base pair of 1. True 2. False 3. False 4. False 5. True DNA is called point mutation. Example is sickle 6. True 7. False 8. True cell anaemia. IV. Match the items of Column I with those of 6. Failure of segregation during cell division, Column II: aneuploidy (A) → (v), (B) → (i), (C) → (ii), (D) → (iii), (E) → (iv) 7. Sickle cell anaemia. 98 Biology–12

8. Plants with shorter life cycle give result sooner; 35. Non-disjunction of 21st chromosomes during more generations can be studied in less time, the anaphase results in trisomy. results will be accurate. 36. The trait is sex linked recessive and is 9. Tall and dwarf plants, terminal and axial flowers. passed from mother to son. If X chromosome of 10. Pod shape and colour: Inflated yellow pods mother carries haemo-philic trait, the son will have it and father passes its X chromosome to (dominant) and constricted green pods (recessive) daughter. 11. Flower position terminal or axial and flower 37. Non-disjunction of 21st chromosomes during colour violet or white. anaphase results in trisomy. 12. Human skin colour is controlled by three genes 38. Mother: XhX, Father: XY together, ABC thus considered polygenic. 39. Test cross = 1 13. Three 14. (a) Incomplete dominance. 2 Marks Questions (b) Mendelian monohybrid cross 15. By test cross 40. P1 RR rr 16. 25% Red Pink 17. 50% 18. Homozygous plants bearing violet flower. RX r 19. Incomplete- Co-dominance F1 Rr (Pink) Dominance P2 Rr Rr All progeny is interme- The progeny shows the Pink X Pink diate of the parents. features of both the The progeny shows the parents equally Rr features of both the parents R RR Rr Both parental as well Both parental and co- r Rr rr as intermediate trait dominant trait present Phenotypic ratio : red : pink : white F2 1 : 2 : 1 is evident Genotypic ratio : RR : Rr : rr 20. Recessive allele 21. The parent plant was heterozygous tall with 1 :2 :1 genotype Tt Here a third phenotype is produced which is a 22. Anaphase combination of the phenotypes of both alleles. 23. Axial violet flowers are dominant traits. The gene can become dominant or recessive due 24. When genes are linked, i.e. when genes for two to mutation or modification. The modified allele different characters are present on the same could lead to the production of: chromosome and lie very close to each other.  The normal less efficient enzyme, in this case the gene is equivalent to unmodified allele. 25. Male honey bee is developed from unfertilized egg.  The non-functional enzyme or 26. 16, Mitosis  No enzyme at all, 27. M a l e D r o s o p h i l a h a s o n e X a n d o n e Y  In both these cases phenotype is affected and chromosomes. trait will depend upon unmodified allele. 28. XO type of sex determination exists in grasshopper 41. Male heterogamety: male produces two types of males. gametes. e.g. Human 29. Female of many birds has a pair of dissimilar ZW F e m a l e h e t e r o g a m e t y : f e m a l e p r o d u c e s chromosomes, while the males possess a pair of two types of gametes. e.g. Birds similar ZZ chromosomes. 42. Female heterogamety exists in birds and sex 30. One X chromosome in female is missing. is determined by the fusion of type of gamete 31. Males have one extra X chromosome. produced by female with the gamete of male. This 32. The defect is caused by the substitution of can be shown in the given cross. Glutamic acid (Glu) by Valine (Val) at the Parents Male X Female sixth position of the beta globin chain of the ZZ ZW haemoglobin molecule. Gametes ZZ ZW 33. Autosomal recessive: sickle cell anaemia Autosomal dominant: myotonic dystrophy ZZ ZW ZZ ZW 34. (a) HbA HbS (b) HbSHbS Male Female Male Female Principles of Inheritance and Variation  99