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CBSE Class 12 Pre Board 2019 : Biology - Prelim 2 (St Xavier's Sr. Sec. School, Delhi)

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Pre Board Examination 2019 Std. 12 03-01-2019 Set 2 BIOLOGY Max. Marks : 70 Time : 3 hrs. General Instructions: All questions are compulsory. The question paper consists of four sections A, B, C and D. Internal choice is given in all the sections. A student has to attempt only one of the alternatives in such questions. Section A contains 5 questions of 1 mark each. Section B has 7 questions of 2 marks each. Section C is of 12 questions of 3 marks each Section D has 3 questions of 5 marks each. Wherever necessary, the diagrams drawn should be neat and properly labeled. SECTION A 1. Name the site of fertilization in humans? (OR) The meiocyte of rice has 24 chromosomes. How many chromosomes are present in endosperm of rice? (1) 2. Name the Organism commercially used for the production of single cell protein. (1) 3. What is brood parasitism? (1) 4. Why must a cell be made 'competent' in biotechnology experiments? How does calcium ion help in doing so? (OR) State the role of 'Biolistic gun' in biotechnology experiments. 5. What are the 'molecular scissors' in rDNA technology? What are they used for in rDNA technology? (1) (1) (1) SECTION B 6. What are staminate and pistillate flowers? Name the types of gametes that are formed in staminate and pistillate flowers? 7. Prior to industrialization, there were far more white-winged moths on trees than melanised moths in England. However, after industrialization, the distribution pattern of these two kinds of moths reversed. What does the above observation indicate? Explain giving reasons. (2) 8. What kind of test will you perform to find out whether the given plant is homozygous dominant or heterozygous? Explain your answer with the help of cross. 9. Expand ELISA and LSD? Explain very briefly. (OR) Name the enzyme produced by streptococcus bacterium. Explain its importance in medical sciences. (2) 10. Differentiate between primary and secondary succession. Provide one example of each. (2) 11. What problem was faced in production of insulin by rDNA technology and how was it resolved? (2) (2) (2) (2)

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