CBSE 2026 · Region 2 · Set 1 · Q29 · 4 marks
Gene manipulation is a fast emerging science. It started with the development of recombinant DNA molecules. This technology which mostly involves cutting and pasting of desired DNA fragments is based on two most important discoveries in bacteria - presence of plasmid and restriction endonucleases. The science of r-DNA technology took birth when Cohen and Boyer ($\displaystyle 1973$) were able to produce a piece of gene containing foreign DNA introduced into plasmid of E.coli.(a)Name one core technique of biotechnology that alters the genetic material.(b)What is a plasmid ? Mention its importance in biotechnology.Which gene was isolated by Cohen and Boyer and from which bacteria ?How is the action of exonuclease different from that of endonuclease ?
Gene manipulation is a fast emerging science. It started with the development of recombinant DNA molecules. This technology which mostly involves cutting and pasting of desired DNA fragments is based on two most important discoveries in bacteria - presence of plasmid and restriction endonucleases. The science of r-DNA technology took birth when Cohen and Boyer ($\displaystyle 1973$) were able to produce a piece of gene containing foreign DNA introduced into plasmid of E.coli.
(a)
Name one core technique of biotechnology that alters the genetic material.
(b)
What is a plasmid ? Mention its importance in biotechnology.
Which gene was isolated by Cohen and Boyer and from which bacteria ?
How is the action of exonuclease different from that of endonuclease ?
Marking-scheme solution
(a)
Genetic Engineering / Recombinant DNA Technology
(b)
• Plasmid is an autonomously replicating circular extra chromosomal DNA.
• It is used as a vector to transfer foreign genes into host cells.
Antibiotic resistant gene, Salmonella typhimurium
Exonuclease: Remove the nucleotides from the ends of DNA strand.
Endonuclease: Make cuts at specific positions within DNA strand.
Biotechnology : Principles and ProcessesProcesses of Recombinant DNA TechnologyUnderstandcase_studymedium
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CBSE Class 12 Biology past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.