‘Taq’ polymerase utilized in PCR is a
Taq polymerase isolated from Thermus aquaticus functions as a DNA-dependent DNA polymerase. It uses single-stranded DNA as template and deoxyribonucleoside triphosphates as substrates to synthesize complementary DNA in the 5' to 3' direction, requiring a primer with free 3' hydroxyl group. It does not use RNA as template or synthesize RNA, distinguishing it from reverse transcriptases and RNA polymerases. Its exceptional thermostability allows high activity through denaturation cycles at 94°C, making iterative synthesis possible without fresh enzyme addition during polymerase chain reaction cycling.
Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.