Question

Which of the following statements is true regarding the DNA polymerase used in PCR?

• A. It is used to ligate/join introduced DNA in recipient cells
• B. It serves as a DNA digesting enzyme
• C. It is isolated from a virus
• D. It remains active at high temperatures

Answer 1

The correct option is D It remains active at high temperatures

PCR or polymerase chain reaction is a technique used in molecular biology to create several copies of a certain DNA segment.

In PCR, Taq polymerase is used which is obtained from the bacterium, Thermus aquaticus, which is found in thermal vents.

Since this bacteria survives in high temperatures, its polymerase enzyme has been found to be heat resistant. Since it is a thermostable enzyme, it is used in PCR. This is due to the fact that PCR requires high temperature, around 96℃, during denaturation of DNA strands.

The normal DNA polymerases are likely to get their conformation altered and lose their functional activity at such high temperatures. This would have interfered with the extension step. Taq polymerase confers an advantage over it and helps complete the reaction.

DNA digesting enzymes (DNases) digest the DNA into fragments. Hence, it is not used in PCR reactions, else it would destroy the sample DNA.

DNA ligase enzyme performs the function of ligating or joining the strands of DNA. It helps in joining Okazaki fragments during DNA replication.