Question

The extension step of the PCR where DNA polymerase gets into action happens at 72℃. This is in contrast to what we have learnt where enzymes are said to be functioning at the optimum temperature range of 35 to 40℃. Why is it so?

• A. All DNA polymerases are active at high temperatures
• B. While 36 to 40℃ is the optimum temperature range, 72℃ is a special sweet spot for most enzymes to work
• C. DNA polymerase used in PCR is obtained from a bacteria that thrives in hot springs
• D. The temperature has no role to play in this process

Answer 1

The correct option is C DNA polymerase used in PCR is obtained from a bacteria that thrives in hot springs

Enzymes are biocatalysts which are functional at specific optimum range of temperature.

All DNA polymerases are not active at high temperatures. But the DNA polymerase enzyme used in the PCR is active at high temperatures. This is because it is obtained from an archaebacteria that usually inhabits thermal vents and hot springs. They are heat resistant forms and can thrive in high temperatures. Therefore, they retain optimal functionality even at 72℃ (extension temperature in PCR). Besides, the high temperatures used to denature DNA (which usually range from 92-96℃) also do not denature this enzyme.