CBSE Class 12 Biology Boards 2020 Question Paper Set 01 Solved

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SECTION A
1. Meselson and Stahl carried out centrifugation in CsCl2 density gradient to separate :
(A) DNA from RNA
(B) DNA from protein
(C) The normal DNA from 15N-DNA
(D) DNA from tRNA
 
2. Self-pollination is fully ensured if 1
(A) the flower is bisexual.
(B) the style is longer than the filament.
(C) the flower is cleistogamous.
(D) the time of pistil and anther maturity is different.
OR
Zoospores are the reproductive units to carry asexual reproduction in 
(A) Chlamydomonas
(B) Spirogyra
(C) Yeast
(D) Rhizopus
 
3. Micropropagation can be achieved by 
(A) Self-pollination
(B) Asexual reproduction
(C) Tissue culture
(D) Vegetative propagation
OR
The microbes commonly used in kitchens are 
(A) Lactobacillus and Yeast
(B) Penicillium and Yeast
(C) Microspora and E. coli
(D) Rhizopus and Lactobacillus
 
4. The main barrier that prevents the entry of micro-organisms into our body is
(A) Antibodies
(B) Macrophages
(C) Monocytes
(D) Skin
 
5. Nematode specific genes were introduced into the tobacco host plant using a vector
(A) pBR 322
(B) Plasmid
(C) Bacteriophage
(D) Agrobacterium
 
6. Given below is one of the strands of a DNA segment :
           TACGTACGTACGTACG
3' _________________________________5'
(a) Write its complementary strand.
(b) Write a possible RNA strand that can be transcribed from the above DNA molecule formed.
 
7. Wings of birds and wings of butterflies contribute to locomotion. Explain the type of evolution such organs are a result of.
 
8. It is often observed that the chances of a person suffering from measles in his or her lifetime are low if he or she has suffered from the disease in their early childhood. Justify the statement.
 
9. List the three hormones produced in women only during pregnancy.
What happens to the levels of estrogen and progesterone during pregnancy ?
 
10. A student on a field trip suddenly felt breathlessness and started to sneeze very badly. Name this response and explain what it is due to.
 
11. With the help of a suitable example, explain how cross-breeding is carried out in developing a new breed in animals.
 
12. Name the genus of baculovirus that acts as a biological control agent in spite of being a pathogen. Justify by giving three reasons that make it an excellent candidate for the job.
OR
‘‘Micro-organisms play an important role for the biological treatment of sewage.’’ Justify.
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Previous Year Question Papers: Class 12 Biology

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Are the solutions for CBSE Class 12 Biology Boards 2020 Question Paper Set 01 Solved based on the official CBSE marking scheme?

Yes, the solutions for CBSE Class 12 Biology Boards 2020 Question Paper Set 01 Solved are prepared by subject matter experts as per official marking scheme. Class 12 students will understand the structure of answers and 'step-marks' methodology Biology.

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Yes, where applicable, CBSE Class 12 Biology Boards 2020 Question Paper Set 01 Solved is available in both English and Hindi mediums. All students from Class 12 can access Biology study material in their preferred language.

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