A foreign DNA and plasmid cut by the same restriction endonuclease can be joined to form a recombinant plasmid using
Answer: (D) Ligase. Answer: (D) Ligase Solution: When a foreign DNA and a plasmid are cut with the same restriction endonuclease, the resulting fragments carry identical complementary 'sticky ends'.
- A.Eco RI
- B.Taq polymerase
- C.Polymerase III
- D.Ligase✓
Correct Answer
(D) Ligase
Solution & Explanation
Answer: (D) Ligase Solution: When a foreign DNA and a plasmid are cut with the same restriction endonuclease, the resulting fragments carry identical complementary 'sticky ends'. The enzyme DNA ligase acts on these cut DNA molecules and joins their ends end-to-end to form a recombinant plasmid. EcoRI is a restriction enzyme (cuts, not joins), and the polymerases synthesise DNA rather than seal nicks between fragments. NCERT Reference: Ch 9, p.165, line(s) 9-10 — "with the plasmid vector became possible with the enzyme DNA ligase, which acts on cut DNA molecules and joins their ends."