The DNA polymerase used in conventional PCR is obtained from a thermophilic bacterium. This source is chosen primarily because the enzyme must:

• A Proofread with 3' to 5' exonuclease activity to eliminate all mutations
• B Withstand repeated heating to about 95 degrees C during template denaturation ✓
• C Synthesise RNA primers without a separate primase
• D Function only on RNA templates converted to cDNA

Explanation

Taq DNA polymerase is isolated from Thermus aquaticus, a hot-spring bacterium. Its thermal stability allows it to survive the 94 to 95 degree denaturation step of every cycle, so it need not be replenished after each round. Option A is incorrect because Taq lacks efficient proofreading, which is why high-fidelity polymerases such as Pfu are preferred when sequence accuracy matters. Options C and D describe functions Taq does not perform.

Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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