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CBSE Class 12 Board Exam 2015 : Biology

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SET 1 . Series : SSO/C Code No. - - . Roll No. 57/1 Candidates must write the Code on the title page of the answer-book. - 8 - - - - 26 , - 15 - 10.15 10.15 10.30 - - Please check that this question paper contains 8 printed pages. Code number given on the right hand side of the question paper should be written on the title page of the answer-book by the candidate. Please check that this question paper contains 26 questions. Please write down the Serial Number of the question before attempting it. 15 minute time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period. ( ) BIOLOGY (Theory) : 3 ] [ Time allowed : 3 hours ] : 70 [ Maximum Marks : 70 : (i) - 26 (ii) A 1 5 - , 1 (iii) B 6 10 - I , 2 (iv) C 11 22 - II , 3 (v) D 23 4 (vi) E 24 26 - , 5 (vii) - , 2 , 3 5 - 57/1 1 [P.T.O. General Instructions : (i) There are a total of 26 questions and five sections in the question paper. All questions are compulsory. (ii) Section A contains questions number 1 to 5, Very Short Answer type questions of 1 mark each. (iii) (iv) (v) (vi) (vii) Section B contains questions number 6 to 10, Short Answer type I questions of 2 marks each. Section C contains questions number 11 to 22, Short Answer type II questions of 3 marks each. Section D contains question number 23, Value Based Question of 4 marks. Section E contains questions number 24 to 26, Long Answer type questions of 5 marks each. There is no overall choice in the question paper, however, an internal choice is provided in one question of 2 marks, one question of 3 marks and all the three questions of 5 marks. In these questions, an examinee is to attempt any one of the two given alternatives. A SECTION A 1. mRNA 1 Write the two specific codons that a translational unit of mRNA is flanked by one on either sides. 2. ? 1 State the type of interaction that exists between ticks and dogs. 3. ( ) 1 Write the chromosomal defect in individuals affected with Klinefelter s syndrome. 4. 57/1 2 1 Identify the picture and mention the vegetative part that helps it to propagate. 5. 1 State the economic value of Saccharum officinarum in comparison to S. barberi. B SECTION B 6. 2 State the functions of Ribozyme and release factor in protein synthesis respectively. 7. : (a) cry 1AC (b) RNA (RNAi) 2 Write the functions of (a) cry 1AC gene (b) RNA interference (RNAi) 8. (a) (b) ? CFC CFCs (a) (b) 57/1 O3 2 O2 Earth Expand CFC. How does it reduce ozone to oxygen ? 3 [P.T.O. 9. (i) , (ii) ? , - 2 What happens to corpus luteum in human female if the ovum is (i) fertilized, (ii) not fertilized ? OR Write the difference between the tender coconut water and the thick, white kernel of a mature coconut and their ploidy. 10. ( ) 2 State the evolutionary relationship giving reasons between the thorn of Bougainvillea and tendril of cucurbit. C SECTION C 11. ADA ? 3 Mention the cause of ADA deficiency in humans. How has genetic engineering helped patients suffering from it ? 12. - - 3 Drinking water problem in our urban areas is caused mainly because we fail to protect our water bodies. Explain how accelerated eutrophication chokes our water bodies to death. 13. 57/1 (b) ( ) ? (a) Differentiate between benign and malignant tumours. (b) Why is colostrum a boon to the newborn baby ? (a) 4 3 Z 14. Y X - (a) X (b) Y (c) Z 3 Z Y X This diagram above shows a part of the human female reproductive system. 57/1 (a) Name the gamete cells that would be present in X if taken from a newborn baby. (b) Name Y and write its function. (c) Name Z and write the events that take place here. 5 [P.T.O. 15. ? 3 ? ? How does the study of fossils support evolution ? Explain. OR What does Hardy-Weinberg Principle of equilibrium indicate ? List any two factors that could alter the equilibrium. What would such an alteration lead to ? 16. 3 Mention any two human diseases caused by round worms. Name their causative agents and their mode of transmission into the human body. 17. 18. (a) (b) ? ? (a) Differentiate between exons and introns. (b) What is a plasmid ? Why is it selected as a vector ? ? - ? 3 3 What is ecological succession ? Where and why would the rate of succession be faster in newly created pond or a forest destroyed by a forest fire ? 19. - MOET ? High yielding cattle is a good solution for food enhancement. How does the MOET technology help to increase the herd size ? 57/1 6 3 20. , (a) ? (b) 3 If there is a history of haemophilia in the family, the chances of male members becoming haemophilic are more than that of the female. 21. (a) Why is it so ? (b) Write the symptoms of the disease. ? ? 3 Why do tribes who live in high altitude of Himalayas experience discomfort in respiration ? How do they get adapted to survive in such a situation ? 22. - : (a) (b) (c) 3 Explain the events in a normal woman during her menstrual cycle on the following days : (a) Pituitary hormone levels from 8 to 12 days. (b) Uterine events from 13 to 15 days. (c) Ovarian events from 16 to 23 days. D SECTION D 23. - ? 4 Peer pressure plays a negative role in triggering smoking habits in adolescents. As a school captain list any two activities you would like to organize with the help of senior students of your school and any other two activities you would like your school authorities to organize for the students to tackle this problem. Explain how these activities will help in doing so. 57/1 7 [P.T.O. E SECTION E 24. (a) (b) (a) (b) (a) (b) (a) (b) 25. ( ) ? ? DNA , : A B O - - 5 What is Central dogma ? Who proposed it ? Describe Meselson and Stahl s experiment to prove that the DNA replication is semi-conservative. OR A couple with blood groups A and B respectively have a child with blood group O . Work out a cross to show how it is possible and the probable blood groups that can be expected in their other off-springs. Explain the genetic basis of blood groups in human population. rDNA PCR DNA ? 5 : , 5 (a) (b) Explain the application of rDNA technology to produce insulin. OR (a) Describe the different steps in one complete cycle of PCR. (b) State the purpose of such an amplified DNA sequence. 26. (a) (b) (a) (b) (a) (b) (a) (b) Describe in sequence the process of microsporogenesis in angiosperms. Draw a labelled diagram of a two celled final structure formed. OR Draw a sectional view of a seminiferous tubule of human. Label sertoli cell, spermatagonia and leydig cell on it and write their functions. Explain the role of pituitary and sex hormones in the process of spermatogenesis. __________ 57/1 8

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