Question

Which of the following statements about the 'Klenow fragment' of DNA polymerase-I is correct?

• A. Possesses \(5^{\prime}\rightarrow3^{\prime}\) exonuclease activity
• B. Main function is to synthesize the leading strand of DNA
• C. They join the Okazaki fragments
• D. Possesses \(3^{\prime}\rightarrow5^{\prime}\) exonuclease activity

Hint:

Klenow fragment: DNA Pol I without \(5^{\prime}\rightarrow3^{\prime}\) exonuclease.
Has \(3^{\prime}\rightarrow5^{\prime}\) exonuclease (proofreading).
Used in DNA labeling.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Klenow fragment is a part of DNA polymerase I.
It has specific enzymatic activities.

Step 2: Key Formula or Approach:
No specific formula.
Need to know the properties of Klenow fragment.

Step 3: Detailed Explanation:
Klenow fragment:
- Lacks \(5^{\prime}\rightarrow3^{\prime}\) exonuclease activity (A is incorrect).
- Possesses \(3^{\prime}\rightarrow5^{\prime}\) exonuclease activity (D is correct).
- Possesses \(5^{\prime}\rightarrow3^{\prime}\) polymerase activity.
It is not the main enzyme for leading strand synthesis (that is DNA Pol III).
It does not join Okazaki fragments (DNA ligase does).
Thus, the correct statement is that it possesses \(3^{\prime}\rightarrow5^{\prime}\) exonuclease activity.

Step 4: Final Answer:
Klenow fragment possesses \(3^{\prime}\rightarrow5^{\prime}\) exonuclease activity.
Hence, the correct option is (D).