(Download) CBSE: Class XII Biology Question Paper - 2020

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Question Papers For Board Examinations 2020

Class – XII

Subject – Biology

Subject :- Biology
Class : XII
Year : 2020

SECTION A

1. Meselson and Stahl carried out centrifugation in CsCl2 density gradient to separate : 1
(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 1
(A) Chlamydomonas
(B) Spirogyra
(C) Yeast
(D) Rhizopus

3. Micropropagation can be achieved by 1
(A) Self-pollination
(B) Asexual reproduction
(C) Tissue culture
(D) Vegetative propagation
OR
The microbes commonly used in kitchens are 1
(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 1
(A) Antibodies
(B) Macrophages
(C) Monocytes
(D) Skin

5. Nematode specific genes were introduced into the tobacco host plant using
a vector 1
(A) pBR 322
(B) Plasmid
(C) Bacteriophage
(D) Agrobacterium