CBSE Class 12 Biology Sample Papers 2011 Set A

Section - A

1. The turkey usually produces females for several generations. How is this possible?

2. The meiocyte of an onion plant contains 32 chromosomes. Workout the number of chromosomes Found in its endosperm.

3. The gene I that controls the ABO blood grouping in human beings has three alleles IA, IB and i.

(a) How many different genotypes are likely to be present in the human population ?

(b) Also, how many phenotypes are possibly present ?

4 Pick out the ancestral line of Cycads from the list given below -

Ferns, herbaceous lycopods, seed ferns, and horsetails

5. Name the event in cell division cycle that results in gain or loss of chromosomes.

6. What are cDNA libraries? How are they made?

7. Do eukaryotic cells restriction endonucleases? Justify your answer.

8 What is the role of polyethylene glycol in somatic hybridisation?

Section - B

9 Define Apomixis and Allogamy.

10 Fed up of a large family, a couple wanted to adopt a terminal method of contraception. Describe the process conducted by

the doctor in either of the cases (male / female partner)

OR

A mother of a one year old daughter wanted to space her second child. Her doctor suggested CuT. Explain its contraceptive actions.

11. The human male and female bird are heterogametic while the human female and male bird are homogametic. Why are they called so?

12. What are interferons. Explain its role in providing immunity. Also name the kind of immunity provided by it.

13. What is allergy? Name the antibody responsible for it. Also mention two chemicals released from the mast cells during an allergic reaction.

14. Give reason -

(a) Bottled fruit juices bought from the market are clearer as compared to those made at home.

(b) Large holes are found in “Swiss cheese”.

15. In which parts of the body of the hosts do the following events in the life cycle of Plasmodium take place. Along with the body parts name the hosts too -

(i) Fertilisation

(ii) Development of gametocytes

(iii) Release of sporozoites

(iv) Asexual reproduction

16. What are the latest methods of detection of cancer?

17 Why is the human genome project called a mega project?

18. Explain what is convergent evolution with the help of an example.

Section - C

19. Draw a labelled diagram of the sectional view of a mature pollen grain of angiosperms. Explain the function of any two of its parts.

20 In a pea plant, smooth seed coat is dominant over wrinkled seed coat. What will be the expected ratio of phenotypes of the offspring in a cross between

(i) Heterozygous smooth × Heterozygous smooth

(ii) Heterozygous smooth × Homozygous wrinkled

(iii) Heterozygous smooth × Homozygous smooth

21 A tRNA is charged with aminoacid methionine

(i) Name the process involved in the attachment

(ii) Point out the mRNA codon and anticodon on tRNA for this aminoacid.

(iii) What is heterochromatin?

22. (a) State Hardy Weinberg principle. Name any two factors which affect it.

(b) Draw a graph to show that natural selection leads to directional change.

23. For remaining alert your friend is taking anti sleep pills .How will you deal with this situation?

OR

For building his muscles a friend is taking Neurobol, an anabolic steroid.What advise will you give him?

24. What are biofertilizers? Give 3 examples.

25. A thallasemic child needed repeated blood transfusions got infected by HIV.

(i) Use a rough diagrammatic sketch and arrows to show how the virus increased in number.

(ii) Why did the increased number of the HIV virus deteriorate the child’s immunity?

(iii) Which diagnostic test showed that the infective virus was HIV?

26 What is a bioreactor? Draw a labelled diagram and explain the functioning of a sparged stirred bioreactor

27 Explain with reference to PCR

(a) A specific enzyme helps in amplication in PCR. Name the bacterium from which it is isolated and state how its thermostable nature is helpful.

(b) Explain its use in molecular diagnosi

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