In PCR (Polymerase Chain Reaction), the enzyme used is Taq polymerase, which is a thermostable DNA polymerase isolated from Thermus aquaticus. It can withstand the high temperatures required during denaturation steps of PCR.

DNA polymerase I → normal bacterial enzyme, not heat stable

Reverse transcriptase → makes DNA from RNA (used in RT-PCR)

Restriction endonuclease → cuts DNA, not used for amplification

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