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Biology · 2022 · 3 marks
Biotechnology : Principles and ProcessesProcesses of Recombinant DNA Technology3 marksUnderstandshort answer
CBSE 2022 · Region 1 · Set 1 · Q12
(i) State the role of a selectable marker in r-DNA technology. (ii) Name one such selectable marker which is considered to be useful for E. coli.…
(i)
State the role of a selectable marker in r-DNA technology.
(ii)
Name one such selectable marker which is considered to be useful for E. coli.
(iii)
Give one reason why is it considered to be a useful marker.
OR What are plasmids? How are they different from cloning vectors? Give one example each for a viral and a bacterial cloning vector.
Marking-scheme solution
(i)
Helps in identifying non-transformants from transformants / Recombinants from non Recombinants
(ii)
Genes encoding resistance to antibiotics such as ampicillin / tetracycline/ kanamycin / chloramphenicol / amp \(\displaystyle { }^{\mathrm{R}}\) / tet \(\displaystyle { }^{\mathrm{R}}\)
(iii)
(The normal E. coli cells do not carry resistance against any of these antibiotics.) It helps to identify and select transformants / identification of recombinants.
OR
Plasmids are extra chromosomal self-replicating (double stranded) circular DNA molecules (generally found in bacterial cell)
Plasmid is circular extra chromosomal DNA of bacterial cells whereas cloning vector is a vehicle that carries foreign DNA into another cell.
Bacteriophage, pBR322
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CBSE Class 12 Biology past-paper question from the 2022 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.