Which mechanism helps prevent errors during DNA replication?

• A. Primer synthesis by primase to start DNA synthesis
• B. Unwinding of the DNA double helix by helicase
• C. 5′→3′ polymerase activity of DNA polymerase
• D. 3′→5′ exonuclease proofreading activity of DNA polymerase

Answer: (D)

Verified step by step guidance

1. Understand that DNA replication involves multiple enzymes and mechanisms to ensure accuracy and efficiency.
2. Recognize that primer synthesis by primase and unwinding by helicase are essential steps to initiate replication but do not directly correct errors.
3. Recall that DNA polymerase synthesizes new DNA strands in the 5′→3′ direction, adding nucleotides complementary to the template strand.
4. Focus on the proofreading function of DNA polymerase, which is its 3′→5′ exonuclease activity; this mechanism removes incorrectly paired nucleotides immediately after they are added.
5. Conclude that the 3′→5′ exonuclease proofreading activity of DNA polymerase is the key mechanism that helps prevent errors during DNA replication by correcting mismatches.