SECTION- A
1. How many pollen grains and ovules are likely to be formed in the anther and the ovary of an angiosperm bearing 25 microspore mother cells and 25 megaspore mother cells respectively?
OR
In case of polyembryony, an embryo A develops from the synergids and the embryo B develops from the nucellus. State the ploidy of embryo A and B.
2. Give the scientific name of the source organism from which the first antibiotic was produced.
3. The prophase I stage of meiosis plays a vital role in r-DNA formation. Justify with reason.
4. Name the technique by which Gene expression can be controlled with the help of RNA molecule.
5. Define Diapause
OR
Define Standing Crop
SECTION- B
6. The figure given below represents a molecule present in the body of a mammal -
a) Name the parts labelled ‘a’ and ‘b’ in the molecule shown above.
b) Name the type of cells that produce this molecule.
OR
Life style diseases are increasing alarmingly in India. We are also dealing with large scale malnutrition in the population. Suggest a process by which we can address both these problems. Give any three examples to support your answer.
7. Why does the lac operon shut down some time after the addition of lactose in the medium where E.coli was growing? Why low level expression of lac operon is always required?
8. a) While cloning vectors, which of the two will be preferred by biotechnologists - bacteriophages or plasmids. Justify with reason.
b) Name the first transgenic cow developed and state the improvement in the quality of the product produced by it.
9. Explain the impact of removal of thymus gland on the immune system of a human body.
OR
A farmer maintained beehives in his Brassica field during its flowering season. How will he be benefitted?
10. How do automobiles fitted with catalytic converters reduce air pollution? Suggest the best fuel for such vehicles.
11. State the Mendelian principle which can be derived from a dihybrid cross and not from monohybrid cross.
12. Comment upon the mode of pollination in Vallisneria and Eichhornia which have emergent flowers.
SECTION- C
13. Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with any three examples.
14. The embryo sac in female gametophyte is seven celled and eight nucleated structure. Justify the statement with the help of a labelled diagram.
OR
List the changes that occur when an ovule matures into seed.
15. Compare and contrast the theories of evolution proposed by Darwin and Hugo De Vries.
16. Explain the different steps involved in the secondary treatment of sewage.
OR
Microbes can be used to decrease the use of chemical fertilizers. Explain how this can be accomplished.
17. a) How do DNA fragments migrate and resolve in a Gel electrophoresis?
b) How lane one is different from lane 2, 3 and 4 in the Gel electrophoresis set up?
c) How pure DNA fragments are made observable in the visible light?
18. Suggest and explain the assisted reproductive techniques which will help a couple to have children, where the female had a blockage in the fallopian tube and the male partner had a low sperm count.
19. a) Construct a complete transcription unit with promoter and terminator on the basis of the hypothetical template strand given below:
b) Write the RNA strand transcribed from the above transcription unit along with its polarity.
OR
a) Mention two events in which DNA is unzipped.
b) Predict the consequences when both the template and the coding strands of a DNA segment participate in transcription process?
Please click on below link to downloadCBSE Class 12 Biology Sample Paper 2022 Set D Solved
