During DNA replication, what are two key functions of DNA polymerase?

• A. It unwinds the DNA double helix at the replication fork and relieves supercoiling ahead of the fork.
• B. It separates newly replicated DNA strands and packages them into nucleosomes during S phase.
• C. It synthesizes RNA primers to initiate DNA synthesis and joins Okazaki fragments by sealing nicks in the sugar-phosphate backbone.
• D. It adds nucleotides to the 3′ end of a growing DNA strand and proofreads/corrects mismatched nucleotides using exonuclease activity.

Answer: (D)

Verified step by step guidance

1. Understand the role of DNA polymerase during DNA replication, which primarily involves synthesizing new DNA strands complementary to the template strand.
2. Recognize that DNA polymerase adds nucleotides to the 3' end of the growing DNA strand, meaning it extends the strand in the 5' to 3' direction by forming phosphodiester bonds.
3. Know that DNA polymerase has proofreading ability through its 3' to 5' exonuclease activity, which allows it to remove incorrectly paired nucleotides and reduce replication errors.
4. Distinguish DNA polymerase functions from other enzymes involved in replication, such as helicase (which unwinds DNA) and primase (which synthesizes RNA primers).
5. Summarize the two key functions of DNA polymerase as: (1) adding nucleotides to the 3' end of the new strand, and (2) proofreading and correcting mismatched nucleotides to ensure replication fidelity.