Question

Which of the following is NOT a thermostable polymerase?

• A. pfu polymerase
• B. Taq polymerase
• C. Vent polymerase
• D. DNA polymerase III

Hint:

Thermostable polymerases are essential for PCR because they can withstand the high temperatures needed for DNA denaturation.

Answer 1

The Correct Option is D

DNA polymerase III is not a thermostable enzyme. It is involved in DNA replication in bacteria, but unlike other polymerases such as Taq polymerase, Pfu polymerase, and Vent polymerase, it is not resistant to the high temperatures required for PCR amplification.

(1) Thermostable Polymerases:
- Taq polymerase, Vent polymerase, and Pfu polymerase are examples of thermostable polymerases. These enzymes are derived from heat-loving organisms (thermophiles), allowing them to function at high temperatures, making them ideal for use in PCR.

(2) Why Other Options Are Correct:
- Taq polymerase (Option 2) is a thermostable enzyme commonly used in PCR due to its stability at high temperatures.
- Vent polymerase (Option 3) is another thermostable polymerase used in PCR for high-fidelity applications.
- Pfu polymerase (Option 1) is also thermostable and is often used for high-fidelity PCR applications.

Conclusion: DNA polymerase III is not thermostable and cannot withstand the high temperatures used in processes like PCR, unlike Taq, Vent, or Pfu polymerases.