CBSE Class 12 Biology Sample Paper 2017 Set 07

SECTION A

1. Why do internodal segments of sugarcane fail to propagate vegetatively even when they are in contact with damp soil? 

2. Mention any two probable reasons for rapid rise of population in our country from about 350 million at the time of independence to about 1 billion by the year 2000. 

3. The gene I that controls the ABO blood grouping in human beings has three alleles I^A, I^B 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. State any one reason to explain why RNA viruses mutate and evolve faster than other viruses. 

5. Mention any two measures for prevention and control of alcohol and drug abuse among adolescents. 

6. What would be the impact on the environment around a thermal power plant if its electrostatic precipitator stops functioning? Give a reason. 

7. Why is thermoregulation more effectively achieved in larger animals than in smaller ones? 

8. A plasmid and a DNA sequence in a cell need to be cut for producing recombinant DNA. Name the enzyme which acts as molecular scissors to cut the DNA segments. 

SECTION B

9. Even though each pollen grain has two male gametes, why are at least 10 pollen grains and not 5 pollen grains required to fertilise 10 ovules present in a particular carpel? 

10. When a red flowerd Antirrhinum plant was crossed with a white flowered Antirrhinum plant, the F₁ - offspring had pink flowers. Mention (a) the genotype of F₁ plant and (b) the reason why it did not bear the parental red or white flower colours? 

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