CBSE Board Class 12 Biology Sample Papers 2009

Sample Paper – 2009
Class – XII
Subject – Biology

SECTION A

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

2.Mieocyte of an onion plant contains 32 chromosomes. Workout the number of chromosomes found in its endosperm,  1

3.Mendels law of segregation (one of the law of inheritance) is universally acceptable without any exception. State the law.1 

4.Given below are the pairs of disease and causative organism. Which out of these is not a matching pair and why?
  Filariasis : Wuchereria
  Ringworm: Ascaris
  AIDS:  Human Immuno virus

5.What is LH surge?         1

6.Write down the complementary sequence of the following.    1
              5’--------GAATTC-------3’

7.Why are the offsprings formed by asexual reproduction referred to as clone?  1

8.Give the scientific name of the causative organism of elephantiasis.   1

SECTION B

9.Differentiate between sexual and asexual reproduction.     2

10.Draw a diagram of L.S of an anatropous ovule of an Angiosperm.    2

11.How is milk production regulated by hormones in human female? Explain.  2

12.Why do sons of a haemophilic father never suffer from this trait?   2

13.What are the latest methods of detection of cancer?     2

14.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). 2
OR
A mother of a one year old daughter wanted to space her second child. Her doctor suggested CuT. Explain its contraceptive actions.

15.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  2

16.When a red flowered Antirrhinum plant was crossed with a white flowered Antirrhinum plant, the F1 offspring had pink flowers. Mention the genotype of F1 plant.   2

17.Describe one example of adaptive radiation.

18.Write in brief about the drugs obtained from flowering plants.

SECTION C

19.Describe post fertilization changes in flowering plants.     3

20.What are chasmogamous flowers? Can cross pollination occur in cleistogamous flowers? Give reasons for your answers. 3

21.In case of sexually transmitted diseases (STDs), what precautions should be taken to prevent it? 3

22.Write a short note on Genetic Code.         3

23.Illustrate schematically the process of initiation, elongation and termination during transcription of a gene in a bacterium.  3

24.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.
Heterozygous smooth X heterozygous smooth
Heterozygous smooth X heterozygous wrinkled
Heterozygous smooth X homozygous smooth.      3

25.Explain in brief: Splicing, capping and tailing.      3

26.Explain in brief Lac Operon.        3

27.Explain in brief events of Menstrual cycle.      3

SECTION D

28.Give reasons for –
Both strands of DNA are not copied during transcription transcription and translation is bacteria can be coupled.
OR
Stanley Miller performed an experiment by recreating in the lab, the probable conditions of the atmosphere of the primitive earth.
What was the purpose of the experiment? What is biogenesis?
Give diagrammatic representation of Miller’s experiment.    5

29.When and where does spermatogenesis in a human male begin to take place? With the help of schematic labeled diagrams trace the development of the mature spermatozoa in a human male. Describe the structure of a human sperm
OR
Show diagrammatically the stages of embryonic development from zygote upto implantation in humans.          5

30.i)What are the three types of RNA
ii) Which one of these has the shape of the clover leaf in two-dimensional structure.
iii) How is each RNA related in the information flow during protein synthesis
OR
Explain Human Genome Project and write down important goals of HGP