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ISC Class Prelims 2021 : Biology (Delhi Public School (DPS), Newtown, Kolkata)

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DELHI PUBLIC SCHOOL NEWTOWN SESSION 2020-21 PREBOARD (ONLINE) EXAMINATION CLASS: XII SUBJECT: BIOLOGY FULL MARKS: 50 TIME: 1HOUR 45 MINUTES Instructions: (Candidates are allowed additional 15 minutes for only reading the paper. They must NOT start writing during this time) This paper comprises Two parts Part I and Part II. Part I contains 10 questions of 1 mark each. All questions are compulsory. Part II consists of Sections A, B and C. Section A contains five questions of two marks each. All questions are compulsory. Section B contains five questions of three marks each, and Section C contains three questions of five marks each. Internal choices have been provided in two questions in Section B and in all three questions of Section C. This paper comprises of three pages. Part-I (10 MARKS) Question 1. Answer the following questions briefly and to the point: i. ii. iii. iv. v. vi. vii. viii. ix. x. [10 1] Give a significant point of difference between Oestrous and Menstrual cycle. Give the biological name of the organism causing Amoebiasis. If the haploid number of chromosomes in a plant species is 20, how many chromosomes will be present in the cells of the shoot tip? Define the following: i. Biopatent ii. Apomixis Name the diagnostic test for AIDS. Fill in the blanks: ___________________ is used to detect DNA bands under UV light on the gel after electrophoresis. Give reasons for the following: Single Cloning site is preferred in a Vector. Differentiate between: Genomic DNA and cDNA. Mention the contribution/s of the following scientists: a. Temin and Baltimore. b. Jacob, Monod and Lwoff Expand the following: a. SSBP b. VNTRs 1 Part-II Section-A (10 Marks) Question 2. If the mother is a carrier of colour blindness and the father is normal, show the possible genotype and phenotype of the offspring of the next generation, with the help of a Punnet square. [2] Question 3. Draw a neat and well-labelled diagram of an antibody molecule. Why is an antibody represented as H2L2 ? [2] Question 4. Give one significant difference between each of the following pairs : (a) Humoral immunity and Cell-mediated immunity. (b) Benign tumour and malignant tumour. [2] Question 5. What is reproductive fitness? Explain it with the help of an example. [2] Question 6. Give one significant difference between primary lymphoid organs and secondary lymphoid organs. Give one example of each. [2] Section-B (15 Marks) Question 7. Draw a neat and well-labelled diagram of L.S. of Anatropous ovule [3] Question 8. (a) Explain the Rivet Popper hypothesis. [3] Or (b) With the help of a suitable diagram and relevant example describe the logistic population of growth curve. [3] Question 9. Give the biological names of the following: (i) The mould from which penicillin is obtained. (ii) Baker s yeast. (iii) The microbe used to control insect larvae growing on cotton. (iv) The microbe used to produce Cephalosporin (v) The fungus that is being developed as a bio-control agent. (vi) A symbiotic nitrogen-fixing bacterium found in root nodules. 2 [3] Question 10. Explain the different types of endosperms in angiosperms. [3] Question 11. (a) Explain the process of sex determination in honey bees. Or (b) Mention the types of sex-determination mechanisms the following crosses show. Give an [3] example of each type and explain the process of sex-determination in any one of these type. i. Female XX with Male XO ii. female ZW with Male ZZ [3] Section-C (15 Marks) Question 12. a) What does PCR stand for? Describe the different steps of PCR. [5] Or (b) How did the process of RNA interference help to control the nematode from infecting the roots of tobacco plants? Explain the detailed mechanism of RNAi. [5] Question 13. a) (i) Give an account of the Blue-White Method of selection of recombinants. (ii) Explain the mechanism of action of restriction endonucleases that makes them suitable for genetic engineering. [3+2] Or (b) (i) Explain what are the desirable characteristics of an ideal cloning vector used in r DNA technology. (ii) Describe two vector less methods of gene transfer used in rDNA technology. [3+2] Question 14 (a) Discuss the various In-situ and Ex-situ strategies for conservation of biodiversity. Or (b) Describe the physico-chemical events that take place during fertilization in human. 3 [5] [5]

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