Question

What are the requirements for a DNA polymerase used in PCR?

Answer 1

The primary requirements for a DNA polymerase used in PCR are optimal activity at temperatures around 75*C and ability to retain that activity after prolonged incubation at even higher temperatures.

Explanation:

PCR requires a DNA polymerase enzyme that makes new strands of DNA, using existing strands as templates.

The DNA polymerase typically used in PCR is called Taq polymerase and is isolated from the heat tolerant bacterium Thermis aquaticus. T. aquatic lives in hot springs and hydrothermal vents. It's DNA polymerase is very heat stable and is most active around 70*C. This heat stability makes Taq polymerase ideal for PCR, as high temperature is used repeatedly in PCR to denature the template DNA, or separate its strands.
Pfu DNA polymerase from Pyrococcus furiosus is also used because of its higher fidelity when copying DNA.