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Board Paper of Class 12-Science 2009 Biology Delhi(SET 1) - Solutions

General Instructions:
(i) All questions are compulsory.
(ii) This question paper consists of four Sections A, B, C and D. Section A contains 8 questions of one mark each, Section B is of 10 questions of two marks each, Section C is of 9 questions of three marks each and Section D is of 3 questions of five marks each.
(iii) There is no overall choice. However, an internal choice has been provided in one question of 2 marks, one question of 3 marks and two questions of 5 marks weightage. A student has to attempt only one of the alternatives in such questions.
(iv) Wherever necessary, the diagrams drawn should be neat and properly labelled.
  • Question 1

    Why hnRNA is required to undergo splicing?

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  • Question 2

    The microscopic pollen grains of the past are obtained as fossils. Mention the characteristic of the pollen grains that makes it happen.

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  • Question 3

    How does colostrum provide initial protection against diseases to newborn infants?

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  • Question 4

    Name the unlabelled areas ‘a’ and ‘b’ of the pie chart (given above) representing the global biodiversity of invertebrates showing their proportionate number of species of major taxa.

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  • Question 5

    Mention the type of evolution that has brought the similarity as seen in potato tuber and sweet potato.

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  • Question 6

    Name the group of organisms and the substrate they act on to produce biogas.

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  • Question 7

    Mention the pollinating agent of an inflorescence of small dull-coloured flowers with well-exposed stamens and large feathery stigma. Give any one characteristic of pollen grains produced by such flowers.

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  • Question 8

    Name the organism commercially used for the production of single-cell protein.

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  • Question 9

    Explain the contribution of Thermus aquaticus in the amplification of a gene of interest.

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  • Question 10

    (i) What does the above diagram illustrate?

    (ii) Name the parts labelled ‘a’ and ‘b’?

    (iii) Name the type of cells that produce this molecule.

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  • Question 11

    Banana is a parthenocarpic fruit whereas oranges show polyembryony. How are they different from each other with respect to seeds?

    OR

    Where are fimbriae present in a human female reproductive system? Give their function.

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  • Question 12

    How is the translation of mRNA terminated? Explain.

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  • Question 13

    Explain accelerated eutrophication. Mention any two consequences of this phenomenon.

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  • Question 14

    List the specific symptoms of Amoebiasis. Name the causative organism.

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  • Question 15

    A crane had DDT level as 5 ppm in its body. What would happen to the population of such birds? Explain giving reasons.

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  • Question 16

    Describe the responsibility of GEAC, set up by the Indian Government.

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  • Question 17

    During the secondary treatment of the primary effluent how does the significant decrease in BOD occur?

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  • Question 18

    Study the figure given below and answer the questions:

    (a) How does the repressor molecule get inactivated?

    (b) When does the transcription of lac mRNA stop?

    (c) Name the enzyme transcribed by the gene ‘Z’.

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  • Question 19

    Name the pioneer species on a bare rock. How do they help in establishing the next type of vegetation? Mention the type of climax community that will ultimately get established.

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  • Question 20

    Study the figure given below and answer the questions that follow:

    (a) Name the stage of human embryo the figure represents.

    (b) Identify ‘a’ in the figure and mention its function.

    (c) Mention the fate of the inner cell mass after implantation in the uterus.

    (d) Where are the stem cells located in this embryo?

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  • Question 21

    Give the scientific name of the parasite that causes malignant malaria in humans. At what stage does this parasite enter the human body? Trace its life cycle in the human body.

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  • Question 22

    Draw a labelled schematic sketch of replication fork of DNA. Explain the role of the enzymes involved in DNA replication.

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  • Question 23

    Explain the causes of global warming. Why is it a warning to mankind?

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  • Question 24

    Haemophilia is a sex-linked recessive disorder of humans. The pedigree chart given below shows the inheritance of haemophilia in one’s family. Study the pattern of inheritance and answer the question given.

    (a) Give all the possible genotypes of the members 4, 5 and 6 in the pedigree chart.

    (b) A blood test shows that the individual 14 is a carrier of haemophilia. The member numbered 15 has recently married the member numbered 14. What is the probability that their first child will be a haemophilic male?

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  • Question 25

    (a) Mention the specific geographical region where these organisms are found.

    (b) Name and explain the phenomenon that has resulted in the evolution of such diverse species in the region.

    (c) Explain giving reasons the existence of placental wolf and Tasmanian wolf sharing the same habitat.

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  • Question 26

    (a) Identify the selectable markers in the diagram of E. coli vector shown above.

    (b) How is the coding sequence of α − galactosidase considered a better marker than the ones identified by you in the diagram? Explain.

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  • Question 27

    Construct an ideal pyramid of energy when 1,000,000 joules of sunlight is available. Label all its trophic levels.

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  • Question 28

    Explain with the help of a diagram the development of a mature embryo sac from a megaspore mother cell in angiosperm.

    OR

    Study the following flow chart. Name the hormones involved at each stage. Explain their functions.

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  • Question 29

    (a) Explain the experiment performed by Griffith on Streptococcus pneumoniae. What did he conclude from this experiment?

    (b) Name the three scientists who followed up Griffith’s experiments.

    (c) What did they conclude and how?

    OR

    Two blood samples A and B picked up from the crime scene were handed over to the forensic department for genetic fingerprinting. Describe how the technique of genetic fingerprinting is carried out. How will it be confirmed whether the samples belonged to the same individual or to two different individuals?

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  • Question 30

    One of the main objectives of biotechnology is to minimise the use of insecticides on cultivated crops. Explain with the help of suitable example how insect-resistant crops have been developed using techniques of biotechnology.

    OR

    (a) How is mature insulin different from proinsulin secreted by pancreas in humans?

    (b) Explain how human functional insulin was produced using rDNA technology.

    (c) Why is the functional insulin thus produced considered better than the ones used earlier by diabetic patients?

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