Molecular Basis of Inheritance 73 70. A single strand of nucleic acid tagged with a radioactive molecule is called : (a) Vector (b) Selectable marker (c) Plasmid (d) Probe 71. If one strand of DNA has the nitrogenous base sequence as ATCTC, what would be the complementary RNA strand sequence ? (a) TTAGU (b) UAGAG (c) AACTG (d) ATCGU 72. Removal of introns and joining of exons in a defined order during transcription is called : (a) Looping (b) Inducing (c) Slicing (d) Splicing 73. Which one of the following is a wrong statement regarding mutations ? (a) Deletion and insertion of base pairs cause frame shift mutations. (b) Cancer cells commonly show chromosomal aberrations. (c) UV and Gamma rays are mutagens (d) Change in a single base pair of DNA does not cause mutation 74. Read the following four statements (1–4) (1) In transcription, adenosine pairs with uracil (2) Regulation of lac Operon by repressor is referred to as positive regulation (3) The human genome has approximately 50,000 genes. (4) Haemophilic is a sex linked recessive disease. How many of the above statements are right ? (a) Two (b) Three (c) Four (d) One 75. What is it that forms the basis of DNA fingerprinting ? (a) The relative proportions of purines and pyrimidines in DNA. (b) The relative difference in the DNA occurrence in blood, skin and saliva. (c) The relative amount of DNA in the ridges and grooves of the fingerprints. (d) Satellite DNA occurring as highly repeated short DNA segments 76. Which enzyme/s will be produced in a cell in which there is a nonsense mutation in the Lac y gene ? (a) Lactose permease and transacetylae (b) -galactosidase (c) Lactose permease (d) Transacetylabe 77. The diagram shows an important concept in the genetic implication of DNA. Fill in the blanks A to C. (a) A - Translation B - extension C - Rosalind Franklin. (b) A - Transcription B - replication C - James Watson.
74 Biology-XII (c) A - Translation B - transcription C - Erwin Chargaff. (d) A - Transcription B - translation C - Francis Crick. 78. The double helix of DNA is made of polynucleotide chains where in backbone is constituted by sugar phosphate and the bases are projected: (a) Inside (b) Outside (c) One base inside and the other outside. (d) Bases remain in line of sugar phosphate. 79. Among the RNA polymerases, the RNA polymerase II transcribes. (a) r-RNA (b) t-RNA (c) Sn-RNA (d) hn-RNA 80. The distance between two nucleotides in a strand of DNA molecule is (a) 3.4 Aº (b) 4.3 Aº (c) 20 Aº (d) 36 Aº 81. Transformation was discovered by (b) Watson and Crick (a) Griffith (c) Meselson and Stall (d) Harshey and Chase 82. Which one of the following is wrongly matched? (a) Repressor protein – Binds to operator to stop enzyme synthesis. (b) Operon – structural genes, operator and promoter. (c) Transcription – writing information from DNA to t‑RNA. (d) Translation – using information in m-RNA to make protein. 83. Select the correct option Direction of RNA Synthesis Direction of Reading of the Template DNA Strand (a) 5′ – 3′ 5′ – 3′ (b) 3′ – 5′ 3′ – 5′ (c) 5′ – 3′ 3′ – 5′ (d) 3′ – 5′ 5′ – 3′ 84. Commonly used vectors for human genome sequencing are (a) Expression vectors (b) T/A cloning vectors (c) T. DNA (d) BAC and YAC 85. An abnormal human baby with xxx sex chromosomes was born due to. (a) Fusion of two ova and one sperm (b) Fusion of two sperms and one ovum (c) Formation of abnormal sperms in the father (d) Formation of abnormal ova in the mother
Molecular Basis of Inheritance 75 86. In sea urchin DNA which is double stranded, 17% of the bases were shown to be cytosine. The percentages of the other three bases expected to be present in this DNA are: (a) G 17%, A 33%, T 33% (b) G 8.5%, A 50%, T 24.5% (c) G 34%, A 24.5%, T 24.5% (d) G 17%, A 16.5%, T 32.5% 87. The enzyme used to join the fragments of DNA during the process of replication is (a) DNA polymerase (b) DNA ligase (c) Endonuclease (d) Helicase 88. Semi-conservative replication of DNA was first demonstrated in (a) Escherichia coli (b) Streptococus pneumoniae (c) Drosophila melanogaster (d) Salmonella typhimurium 89. The transfer of genetic material from one bacterium to another via viruses is called (a) Transformation (b) Conjugation (c) Recombination (d) Transduction 90. Triticale is an example of– (b) Allopolyploidy (a) Autopolyploidy (c) Aneuploidy (d) None of the above 91. Bacterial viruses usually have (b) Double stranded RNA (a) Single stranded RNA (c) Single stranded DNA (d) Double stranded DNA 92. Which one of the following is not applicable to RNA ? (a) 5′ phosphonyl and 3′ hydroxyl ends (b) Heterocylic nitrogenous bases (c) Chargaff’s rule (d) Complementary base pairing 93. Satellite DNA is important because it– (a) Shows high degree of polymorphism in population and also the same degree of polymorphism in an individual, which is heritable from parents to children. (b) Codes for enzymes needed for DNA replication. (c) Does not code for proteins and is same in all members of the population. (d) Codes for proteins needed in cell cycle. Answers 1. (b) 2. (b) 3. (c) 4. (d) 5. (a) 6. (b) 7. (a) 8. (d) 9. (a) 10. (c) 11. (b) 12. (c) 13. (c) 14. (d) 15. (c) 16. (b) 17. (a) 18. (d) 19. (c) 20. (d) 21. (b) 22. (a) 23. (c) 24. (b) 25. (b) 26. (a) 27. (a) 28. (a) 29. (b) 30. (d)
76 Biology-XII 31. (b) 32. (b) 33. (d) 34. (c) 35. (a) 36. (c) 37. (d) 38. (b) 39. (d) 40. (b) 41. (a) 42. (d) 43. (c) 44. (a) 45. (a) 46. (c) 47. (a) 48. (a) 49. (b) 50. (a) 51. (d) 52. (c) 53. (c) 54. (a) 55. (d) 56. (a) 57. (c) 58. (c) 59. (b) 60. (a) 61. (c) 62. (a) 63. (b) 64. (b) 65. (c) 66. (a) 67. (a) 68. (d) 69. (a) 70. (d) 71. (b) 72. (d) 73. (d) 74. (a) 75. (d) 76. (b) 77. (d) 78. (a) 79. (d) 80. (a) 81. (a) 82. (c ) 83. (c) 84. (d) 85. (d) 86. (a) 87. (b) 88. (a) 89. (d) 90. (b) 91. (d) 92. (c) 93. (a) Assertion-Reason Type Questions In the following questions a statement of Assertion (A) is followed by a statement of Reason (R). — If both Assertion and Reason are true, and the Reason is the correct explanation of the Assertion, then mark (a). — If both Assertion and Reason are true, and the Reason is not the correct explanation of the Assertion, then mark (b). — If Assertion is true statement but Reason is false, then mark (c). — If both Assertion and Reason are false statements, then mark (d). 1. A. DNA is macromolecule of high molecular weight. R. Amino acids are monomeric units of DNA. 2. A. DNA consists of two complementary polynucleotide chains. R. In two polynucleotide chains, A pairs with T and G pairs with C. 3. A. In a DNA molecule A-T rich proteins melt before G-C rich proteins. R. There are 2H bonds between A and T, whereas 3H bonds are present between G and C. 4. A. tRNA is called adopter RNA. R. RNA carries genetic information from nuclear DNA to cytoplasm for protein synthesis.
Molecular Basis of Inheritance 77 5. A. mRNA is short lived RNA. R. Formation of mRNA from DNA is called transcription. 6. A. rRNAs are smallest molecules of all RNAs. R. tRNAs carries amino acids from cellular pool to the site of protein synthesis. 7. A. In vitro synthesis of DNA was done by A. Kornberg. R. A. Kornberg discovered DNA polymerase enzyme. 8. A. In prokaryotic cells, three distinct types of RNA polymerases are present. R. RNA polymerase in E. coli consists of five polypeptide chains. 9. A. In prokaryotes initiating amino acid methionine is formylated. R. tRNAmet carries methionine to the initiator codon on mRNA. 10. A. Lac operon given by Jacob and Monod is repressible operon. R. The system of regulation in lac operon is always a negative control. 11. A. mRNA attaches itself to ribosome via its 5′ end. R. mRNA has F-capsular nucleotide and basis for lagging sequence. 12. A. Hn mRNA is larger than mRNA. R. Hn RNA has non-translating introns and more exons than required for translation. Answers 1. (c) 2. (a) 3. (a) 4. (c) 5. (b) 6. (d) 7. (b) 8. (c) 9. (b) 10. (d) 11. (b) 12. (d) Matching Type Questions In the following question match the items in Column I with the items in Column II. An item in Column I may match with more than one items in Column II. Match the Terms of Column I with Terms of Column II: Column I Column II (a) Transcription (i) Semi-conservative replication (b) Beadle and Tatum (ii) Synthesis of RNA on DNA template (c) DNA (iii) Synthesis of protein of mRNAs (d) Central dogma (iv) One gene one enzyme hypothesis (e) Translation. (v) DNA → RNA → Polypeptide (a)–(iii) (b)–(i) Answers (d)–(ii) (e)–(iv) (c)–(v)
78 Biology-XII Very Short Answer Type Questions 1. Name the RNA that carries information about the sequence of amino acids in a polypeptide. 2. What is the site of protein synthesis ? 3. What is a codon ? 4. What is an anticodon ? 5. How many bases codes for one amino acid ? 6. Name the amino acids which have only one codon each. 7. Of the 64 possible code triplets, how many code for amino acids and how many for stop signals ? 8. Name the enzyme that can break and reseal one strand of DNA. 9. Name the enzymes that catalyse (i) Replication of DNA (ii) Formation of RNA (iii) Joining of Okazaki segments. 10. What is proofreading in DNA synthesis ? 11. Name three non-sense codons. 12. What is the function of tRNA. 13. What is Chargaff’s rule ? 14. Which molecule bears codons and which molecule anticodons ? 15. Give the two terms used to describe the base triplets on the RNA molecules. 16. If one strand of double stranded DNA has the following sequence 5′ ...... ACC ATT CG ...... 3′ what would be the sequence of the opposite strand in its 5′ to 3′ direction. 17. What is meant by polycistronic mRNA ? 18. Why hnRNA is required to undergo splicing ? 19. When and at what end does the ‘tailing’ of hnRNA take place ? 20. At which ends do ‘capping’ and ‘tailing’ of hnRNA occur respectively ? 21. Mention the two additional processings which hnRNA needs to undergo after splicing so as to become functional.
Molecular Basis of Inheritance 79 22. Name the enzyme involved in the continuous replication of DNA strand. Mention the polarity of template strand. 23. Mention two functions of the codon AUG. 24. Mention the role of the codon AUG and UGA during protein synthesis. 25. Name the enzyme and state its property that is responsible for continuous and discontinuous replication of the two strands of DNA molecule. Answers 1. mRNA 2. Ribosomes 3. A base triplet on mRNA chain. 4. A base triplet at the recognition end of tRNA molecule. 5. Three 6. Methionine and tryptophan 7. 61 : 3 8. Topoisomerases (DNA gyrases) 9. (i) DNA polymerase (ii) RNA polymerase (iii) Ligase 10. Sensing of wrong base pairing during DNA replication and replacing the same with correct one with the help of DNA polymerase. 11. UAA, UAG and UGA. 12. To carry appropriate amino acids to mRNA codons. 13. In a DNA molecule, A = T and G = C 14. mRNA bears codon, tRNA bears anticodon. 15. Codon and anticodon 16. 5´-CGAATGGT-3´ 17. A single stretch of mRNA covering more than one gene. 18. To remove the introns. 19. Just after splicing ; at 3´-end of hnRNA. 20. Capping at 5´-end and tailing at 3´-end of hnRNA. 21. Capping and tailing. 22. DNA dependent DNA polymerase ; 5′ → 3′ polarity. 23. Codes for methionine and also act as initiator codon. 24. AUG acts as initiator codon and UGA acts as stop codon. 25. DNA polymerase: It catalyses polymerisation of the nucleotides only in 5′ → 3′ direction.
80 Biology-XII Fill in the Blanks Fill in the following blanks with appropriate items: 1. One turn of DNA double helix measures ...... Å and contains ...... base pairs. 2. The successive base pairs in DNA double helix are ....... Å apart. 3. A sequence of 3 bases that code for an amino acid is called a ...... . 4. The formation of peptide bond is catalysed by the enzyme ...... . 5. The two enzymes that help in DNA replication are ...... and ...... . 6. Genes that shuffle from one location to another are called ...... . 7. Transfer of information from DNA to mRNA is called ....... . 8. A polysome is a row of ...... on an mRNA chain. 9. New strands of DNA are formed only in the ...... direction. Answers 1. 34, 10, 2. 3.4 3. codon 6. Jumping genes 4. Peptidyl transference 5. DNA polymerase, ligase 9. 5′–3′. 7. Transcription 8. ribosomes True/False Statements State whether the following statements are true or false: 1. The self duplication property of DNA is called replication. 2. RNA is the genetic material in some viruses. 3. Bacterial transformation and viral infection experiments have proved that RNA is the genetic material. 4. Replication of DNA is semi-conservative. 5. The synthesis of RNA molecule from DNA template is called translation. 6. Protein synthesis involves three steps : initiation, elongation and termination of polypeptide chain. 7. Flow of information from DNA to mRNA and thence to a polypeptide is called central dogma in molecular biology. 8. Assembly of an amino acid chain according to the sequence of base triplets in mRNA is called transcription. Answers 1. True 2. True 3. False 4. True 5. False 6. True 7. True 8. False
Molecular Basis of Inheritance 81 Case Study Based MCQs I. Study the given picture and answer the following questions. 6 8 1 2 3 49 7 5 1. What does the given picture show? (b) Blender experiment (a) Translation (synthesis of protein) (c) Chase’s experiment (d) None of these 2. Identify the end marked (1). (b) 2´end (a) 5´end (c) 3´end (d) None of these 3. Name the structure marked as (6). (b) Small sub-unit of ribosome (a) Small sub-unit of anticodon (c) Large sub-unit of ribosome (d) None of these 4. Identify the end marked (2). (b) 5´end (a) 4´end (c) 3´end (d) None of these 5. Name the site marked as (8). (b) A–site (a) P–site (c) Q–site (d) D–site 6. Name the structure marked as (7). (b) Large sub-unit of robosome (a) Large sub-unit of codon (c) Both (a) and (b) (d) None of these 7. Name the structure marked as (5). (b) Sulphuric Acid (a) Amino Acid (c) Both (a) and (b) (d) None of these II. Study the given picture and answer the following questions. i 45 1 2 3 mRNA 78 9 Repressor 6 Lactose
82 (b) Translation Biology-XII (d) None of these 1. What does the given figure indicate? (a) 7. (b) (a) Lac operon (b) Galactose (a) (c) Blander Experiment (d) None of these 2. Name the product marked as (9). (b) Tranacetylase (a) Glucose (d) None of these (c) Both (a) and (b) (b) Lac Z 3. Name the enzymes marked as (8). (d) None of these (a) Permease (c) Both (a) and (b) (b) Permease (d) None of these 4. Name the genes marked as (4). (a) Promoter gene (b) Lac Y (c) Lac Y (d) None of these 5. Name the enzymes marked as (7). (a) -galaclosidase (c) Tranacetylase 6. Name the gene marked as (4). (a) Lac A (c) Promoter gene Answers I. 1. (a) 2. (a) 3. (b) 4. (c) 5. (a) 6. II. 1. (a) 2. (c) 3. (b) 4. (a) 5. (b) 6.
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