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Biology · 2025 · 2 marks
Biotechnology : Principles and ProcessesProcesses of Recombinant DNA Technology2 marksUnderstandvery short answer
CBSE 2025 · Region 7 · Set 3 · Q17
(a) How is DNA isolated in purified form from a bacterial cell?
(a)
How is DNA isolated in purified form from a bacterial cell ?
OR
(b)
Explain how human functional insulin was produced by using recombinant DNA (rDNA) technology.
Marking-scheme solution
-DNA from bacteria can be released from the cells by digesting the cell envelope
with enzyme lysozyme.
-Protein and RNA are removed by treating with proteases and ribonuclease
respectively.
-Other molecules can be removed by appropriate treatments.
-Purified DNA ultimately can be precipitated out after the addition of chilled
ethanol.
-Two DNA sequences coding for the polypeptide A and B have been prepared
(in vitro).
-These DNA sequences were introduced into the plasmid of E. coli to produce the
polypeptides.
-Polypeptide chains ‘A’ and ‘B’ were produced separately in the bacterium.
-They have been extracted and combined by creating disulphide bonds to form
human insulin.
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CBSE Class 12 Biology past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.