Question

Which of the following E. coli DNA polymerase possesses both 5'- and 3'-Exonuclease activity and is thus its own Proofreader and Editor?

• A. DNA Polymerase I
• B. DNA Polymerase II
• C. DNA Polymerase III
• D. DNA Polymerase E

Hint:

DNA Pol I:
- Both 5'\(\rightarrow\)3' and 3'\(\rightarrow\)5' exonuclease.
- DNA Pol III: Only 3'\(\rightarrow\)5' exonuclease (proofreading).
- 5'\(\rightarrow\)3' exonuclease is unique to DNA Pol I.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
This question tests knowledge of E. coli DNA polymerases and their activities.

Step 2: Detailed Explanation:
DNA Polymerase I possesses both 5'\(\rightarrow\)3' and 3'\(\rightarrow\)5' exonuclease activities.
- 5'\(\rightarrow\)3' exonuclease: Removes RNA primers.
- 3'\(\rightarrow\)5' exonuclease: Proofreading activity.
DNA Polymerase III: Main replicative polymerase, has only 3'\(\rightarrow\)5' exonuclease.
DNA Polymerase II: Involved in DNA repair, has proofreading activity.
DNA Polymerase E: Not found in E. coli.
Thus, DNA Polymerase I possesses both activities.

Step 3: Final Answer:
Thus, DNA Polymerase I possesses both 5'- and 3'-exonuclease activities, which corresponds to option (A).
[0.5cm]