NBSE_Biology-12

Class 12  Series NBSE/XII/2023 Code No. 044/12/1 Roll No.  Candidates must write the Code No. on the title page of the Answer sheet. l Please check that this question paper contains 8 printed pages. l Code number given on the right hand side of the question paper should be written on the title page of the Answer sheet. l Please check that this question paper contains 33 questions. l 15 minutes time has been allotted to read this question paper. BIOLOGY Time Allowed : 3 Hours  Max. Marks: 70  General Instructions: (i) All questions are compulsory. (ii) This question paper has four sections: Section A, Section B, Section C and Section D. There are 33 questions in the question paper. (iii) Section–A has 14 questions of 1 mark each and 02 case-based questions. Section–B has 9 questions of 2 marks each. Section–C has 5 questions of 3 marks each and Section–D has 3 questions of 5 marks each. (iv) There is no overall choice. However, internal choices have been provided in some questions. A student has to attempt only one of the alternatives in such questions. (v) Wherever necessary, neat and properly labeled diagrams should be drawn. NBSE 2023 1 P.T.O.

Section-A All questions are compulsory. In case of internal choices, attempt any one of them. I.  Objective Type Questions (1 Mark) Q1. T he theory of spontaneous generation stated that: 1 (a) life arose from living forms only. (b) life can arise from both living and non-living. (c) life can arise from non-living things only. (d) life arises spontaneously, neither from living nor from the non-living. 1 Q2. The bones of forelimbs of whale, bat, cheetah and man are similar in structure, because: (a) one organism has given rise to another (b) they share a common ancestor (c) they perform the same function (d) they have biochemical similarities 1 Q3. The process of mineralisation by micro organisms helps in the release of: (a) inorganic nutrients from humus (b) both organic and inorganic nutrients from detritus (c) organic nutrients from humus (d) inorganic nutrients from detritus and formation of humus. 1 Q4. Which of the following is not a producer? (a) Spirogyra (b) Agaricus (c) Volvox (d) Nostoc II.  Very Short Answer Type Questions (1 Mark) Q5. Name the types of synthesis ‘a’ and ‘b’ occurring in the replication fork of DNA as shown below: 1 Q6. Name an IUD that you would recommend to promote the cervix hostility to the sperms. 1 Q7. State a difference between a gene and an allele. 1 Q8. On what basis is the skin colour in humans considered polygenic? 1 Q9. Name the components ‘a’ and ‘b’ in the nucleotide with a purine given below: 1 NBSE 2023 2

Q10. Name the interaction that exists between sucker fish and shark. 1 Q 11. Assertion (A): b-cells work chiefly by secreting substances called antibodies into the body fluids. 1 Reason (R): Antibodies ambush foreign antigen circulating in the blood stream. (a) Both assertion and reason are true, and reason is the correct explanation of assertion. (b) Both assertion and reason are true, but reason is not the correct explanation of assertion. (c) Assertion is true but reason is false. (d) Both assertion and reason are false. OR Assertion (A): All endonuclease cut DNA at specific sites. Reason (R): Endonucleases are found in viruses. (a) Both assertion and reason are true, and reason is the correct explanation of assertion. (b) Both assertion and reason are true, but reason is not the correct explanation of assertion. (c) Assertion is true but reason is false. (d) Both assertion and reason are false. Q12. Assertion (A): Interferons help in the elimination of viral infections. Reason (R): Interferons released by infected cells, reach nearby unaffected cells and make them resistant to viral infection. 1 (a) Both assertion and reason are true, and reason is the correct explanation of assertion. (b) Both assertion and reason are true, but reason is not the correct explanation of assertion. (c) Assertion is true but reason is false. (d) Both assertion and reason are false. Q 13. Assertion (A): Besides curdling of milk, LAB also improve its nutritional quality by increasing vitamin-B12. Reason (R): LAB, when present in human stomach, check disease causing microbes. 1 (a) Both assertion and reason are true, and reason is the correct explanation of assertion. (b) Both assertion and reason are true, but reason is not the correct explanation of assertion. (c) Assertion is true but reason is false. (d) Both assertion and reason are false. Q14. Assertion (A): Restriction endonucleases are also called ‘molecular scissors’. Reason (R): When fragments generated by restriction endonucleases are mixed, they join together due to their sticky ends. 1 (a) Both assertion and reason are true, and reason is the correct explanation of assertion. (b) Both assertion and reason are true, but reason is not the correct explanation of assertion. (c) Assertion is true but reason is false. (d) Both assertion and reason are false. Read the following and answer any four questions from 15(i) to 15(v) given below: Q 15. AIDS was first reported in 1981. Which causes immune system becomes non-functional during lifetime. It is called syndrome because body shows group of symptoms of different diseases. Causative organism is Human Immuno Deficiency Virus (HIV). It is a retrovirus and its genetic material is RNA. The time period between infection and first appearance of symptoms may be from 5-10 years. AIDS is transmitted via unprotected sexual contact, using infected hypodermic needles, blood transfusion and from mother NBSE 2023 3 P.T.O.

to unborn child via placenta. Risk of infection increases in the following cases: Individual has multiple partners, drug addicts as they share hypodermic needles and repeated blood transfusion. AIDS is diagnosed by Enzyme Linked Immuno-Sorbant Assay (ELISA). Anti-retroviral drugs are partially effective, only can prolong life but cannot prevent death. 4 (i) HIV first recognized in the U.S. in: (a) 1984 (b) 1975 (c) 1981 (d) 1972 (ii) Select correct symptom of HIV infection: (a) Swollen lymph nodes (b) Fever (c) Tiredness (d) All of the above (iii) HIV attacks which cell in the immune system? (a) Epithelial cells (b) White blood cells called T cells (c) Red blood cells (d) Platelets (iv) The CD4 T-cell count in AIDS infectedperson: (a) Below 50 per cubic milliliter (b) Below 1,000 per cubic milliliter (c) Below 200 per cubic milliliter (d) Below 500 per cubic milliliter (v) Assertion (A): AIDS virus enters helper T-lymphocytes (TH) and produces its progeny after destroying the helper T-lymphocyte. Reason (R): New virus again attacks helper T-lymphocytes and number of which ultimately decreases. (a) Both assertion and reason are true, and reason is the correct explanation of assertion. (b) Both assertion and reason are true, but reason is not the correct explanation of assertion. (c) Assertion is true but reason is false. (d) Both assertion and reason are false. Read the following and answer any four questions from 16(i) to 16(v) given below: Q 16. According to physicist, George Gamow, the genetic code is a set of three-letter combinations of nucleotides (triplet) called codons, each of which codes for a specific amino acid or stop signal. As there are only four bases and if only one base codes for an amino acid, they will code for only 4 amino acids. If the code for an amino acid is doublet, there will be 16 possible combinations so they will code for only 16 amino acids. But if the code is triplet, 64 combinations are possible. This will cover all twenty amino acids. Dr. Har Gobind Khorana synthesized synthetic RNA molecules by using three repeating units with defined combinations of bases, homopolymers and copolymers. Khorana was the first scientist to chemically synthesize oligonucleotides. He also identified stop codons. Marshall Nirenberg developed cell free system to synthesize proteins by adding poly uracil RNA to the system. This proved that genetic code is a triplet. Discovery of Servo Ochoa enzyme, a polynucleotide phosphorylase also helped synthesizing RNA in template independent manner. 4 (i) Which of the following is incorrect about the genetic code? (a) Ambiguous (b) Non-overlapping (c) Triplet (d) Degenerate (ii) The codon is a ………… (a) Singlet (b) Duplet (c) Triplet (d) Quadruplet (iii) Which of the following is not a termination codon? (a) UGA (b) AGA (c) AGG (d) UAC (iv) The wobble hypothesis was devised by ………… (a) Arthur Kornberg (b) Francis Crick (c) James Watson (d) William Asbury NBSE 2023 4

(v) The genetic code is a set of three-letter combinations of nucleotides called (a) Codons (b) Coding (c) Combinations (d) None of these Section-B Q17. A single pea plant in your kitchen garden produces pods with seeds, but the individual papaya plant does not. Explain.  2 Q 18. Following are the features of the genetic codes. What does each one indicate? 2 Stop codon; Unambiguous codon; Degenerate codon; Universal codon. Q19. Suggest four important steps to produce a disease resistant plant through conventional plant breeding technology. 2 Q 20. In view of the current food crisis, it is said, that we need another green revolution. Highlight the major limitations of the earlier green revolution. 2 OR Enumerate, in sequential order, the four steps that a plant breeder should know to obtain a disease resistant crop. Q21. Female reproductive organs and associated functions are given below in column A and B. Fill the blank boxes. 2 Column A Column B Ovaries Ovulation Oviduct a b Pregnancy Vagina Birth OR From where the parturition signals arise-mother or foetus? Mention the main hormone involved in parturition. Q22. Where are fimbriae present in human female reproductive system? Give their function. 2 Q 23. Both a wine maker and a molecular biologist who had developed a recombinant vaccine claim to be biotechnologists. Who in your opinion is correct? 2 Q24. What is meant by the term ‘breed’? What are the objectives of animal breeding? 2 Q 25. Plants that inhabit a rain-forest are not found in a wetland. Explain. 2 Section-C Q26. What is mutualism? Mention any two examples where the organisms involved are commercially exploited in agriculture. 3 Q27. Suggest and describe a technique to obtain multiple copies of a gene of interest in vitro. 3 Q 28. What are the changes in the oogonia during the transition of a primary follicle to Graafian follicle? 3 Q 29. Biotechnology has helped farmers to get pest resistant cotton crops. Explain the technique adopted along with its mode of action. (Mention six points) 3 Q30. In the given flow diagram, the replication of retrovirus in a host is shown. Observe and answer the following questions. 3 (a) Fill in (1) and (2) NBSE 2023 5 P.T.O.

(b) Why is the virus called retrovirus? (c) Can the infected cell survive while viruses are being replicated and released? OR Given below is a flow chart showing ovarian changes during menstrual cycle. Fill in the spaces giving the name of the hormones responsible for the events shown. Section-D Q31. Represent schematically the life cycle of a malarial parasite. 5 OR Compare the life style of people living in the urban areas with those of rural areas and briefly describe how the life style affects their health. Q 32. (a) How are the following formed and involved in DNA packing in a nucleus of a cell? 5 (i) Histone octamer (ii) Nucleosome (iii) Chromatin (b) Differentiate between Euchromatin and Heterochromatin. NBSE 2023 6

OR Explain the role of lactose as an inducer in a lac operon. Q33. (a) Why should we conserve biodiversity? How can we do it? 5 (b) Explain the importance of biodiversity hot spots and sacred groves. OR (a) Represent diagrammatically three kinds of age-pyramids for human populations. (b) How does an age pyramid for human population at given point of time help the policy makers in planning for future? rrr NBSE 2023 7 P.T.O.

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