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Biology · 2026 · 4 marks
Biotechnology : Principles and ProcessesProcesses of Recombinant DNA Technology4 marksApplycase study
CBSE 2026 · Region 5 · Set 1 · Q30
Read the following passage and answer the questions that follow: We know that plasmids and bacteriophages are the most commonly used vectors in…
Read the following passage and answer the questions that follow : We know that plasmids and bacteriophages are the most commonly used vectors in biotechnology experiments. If we can link an alien piece of DNA to the plasmid DNA, the alien DNA can be multiplied equal to the copy number of the plasmid. Engineered vectors are used these days. Study the diagram of the E. coli cloning vector pBR322 and answer the questions that follow :
(a)
Why are plasmids and bacteriophages used as cloning vectors ?
(b)
(i)
Identify :
(I)
The gene in the cloning vector that controls the copy number of the vector.
(II)
The restriction site - C in the 'rop' gene.
OR
(ii)
Identify and name two selectable markers shown in the diagram.
(c)
Name the two restriction sites each in the two genes you have identified as selectable markers.
Marking-scheme solution
(a)
Plasmids and bacteriophages have the ability to replicate / They multiply within the bacterial cells independently of the chromosomal DNA / an alien piece of
DNA can be ligated to them / They can be multiplied equal to their specific copy numbers.
(b)
(i)
(I)
ori
(II)
Pvu II
OR
(ii)
G : ampR /ampicillin-resistance gene, H : tetR/ tetracycline-resistance gene.
(c)
Pst I , Pvu I, BamH I, Sal I
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CBSE Class 12 Biology past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.