Question

Which of the following activity is not present in Taq polymerase?

• A. 5'–3' polymerase
• B. 5'–3' exonuclease
• C. 3'–5' exonuclease
• D. Both 5'–3' polymerase and 5'–3' exonuclease

Hint:

Taq polymerase lacks proofreading ability because it does not have 3'–5' exonuclease activity, making it prone to errors during amplification.

Answer 1

The Correct Option is C

Step 1: Understanding Taq polymerase.
Taq polymerase is a thermostable DNA polymerase used in the polymerase chain reaction (PCR) to amplify DNA. It has several key activities: 5'–3' polymerase activity, which allows it to synthesize DNA, and 5'–3' exonuclease activity, which allows it to degrade DNA. However, Taq polymerase lacks 3'–5' exonuclease activity, which is present in some other polymerases for proofreading.
Step 2: Analyzing the options.
(1) 5'–3' polymerase: This is present in Taq polymerase. It is responsible for adding nucleotides during DNA synthesis.
(2) 5'–3' exonuclease: This is present in Taq polymerase. It allows for the degradation of DNA.
(3) 3'–5' exonuclease: Correct — Taq polymerase lacks 3'–5' exonuclease activity, which is responsible for proofreading during DNA synthesis.
(4) Both 5'–3' polymerase and 5'–3' exonuclease: This is incorrect. Both of these activities are present in Taq polymerase.
Step 3: Conclusion.
The correct answer is (3) 3'–5' exonuclease, as Taq polymerase does not have proofreading activity.