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Biology · 2026 · 2 marks
Biotechnology : Principles and ProcessesProcesses of Recombinant DNA Technology2 marksUnderstandvery short answer
CBSE 2026 · Region 5 · Set 1 · Q20
(a) Suggest how a virus-free healthy plant can be obtained from a diseased sugarcane plant.
(a)
Suggest how a virus-free healthy plant can be obtained from a diseased sugarcane plant.
OR
(b)
In order to force bacteria to take up the recombinant DNA, they must be made competent. Explain how it can be achieved.
Marking-scheme solution
(a)
The meristem is removed from a diseased plant, and grown in-vitro / by tissue
culture method plant produced is virus free.
OR
(b)
− Treat the bacterial cells with a specific concentration of a divalent cation such as Ca ++.
− Incubating bacteria (host) with recombinant DNA on ice.
− Place them at 420C / give heat shock at 420C
− Put them back on ice this enables the bacteria to take up the recombinant DNA.
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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.