Question

Klenow fragment is derived from __________.

• A. DNA ligase
• B. DNA Polymerase I
• C. Reverse transcriptase
• D. DNA Polymerase III

Hint:

This fragment is created by removing the 5' to 3' exonuclease domain from a specific bacterial polymerase.

Answer 1

The Correct Option is B

Step 1: The Klenow fragment is a large protein fragment obtained by proteolytic cleavage of E. coli DNA Polymerase I.

Step 2: This cleavage removes the small N-terminal domain responsible for 5' to 3' exonuclease activity while retaining the polymerase (5' to 3' synthesis) activity and the 3' to 5' proofreading exonuclease activity, making it very useful in molecular biology techniques like filling in sticky ends and labelling DNA.

Step 3: DNA ligase seals nicks in the DNA backbone, reverse transcriptase synthesizes DNA from an RNA template, and DNA Polymerase III is the main replicative polymerase in bacteria, none of which is the source enzyme for the Klenow fragment.

Step 4: So the correct answer is DNA Polymerase I.