Practice question

Taq polymerase isolated from Thermus aquaticus is highly processive and thermostable but lacks 3' to 5' exonuclease activity associated with proofreading. Consequently, mismatched nucleotides incorporated during synthesis are not excised and corrected, resulting in higher error rate of approximately 1×10⁻⁴ to 2×10⁻⁵ per base per duplication. This deficiency is acceptable for routine detection and cloning where fidelity requirement is moderate, but problematic for high-fidelity cloning and sequencing. Alternatives such as Pfu, Vent/Tli, and Q5 possess intrinsic proofreading and provide superior accuracy.