In the overview of DNA replication, which pair best describes the two key functions of DNA polymerase during replication?

• A. It binds to the origin of replication and prevents the re-annealing of separated DNA strands.
• B. It unwinds the DNA double helix and relieves supercoiling ahead of the replication fork.
• C. It lays down RNA primers to initiate synthesis and seals nicks between Okazaki fragments.
• D. It synthesizes new DNA by adding nucleotides to the 3′ end of a growing strand and proofreads/corrects mismatched bases (exonuclease activity).

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the role of DNA polymerase in DNA replication. DNA polymerase is the enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template strand.
2. Step 2: Recognize that DNA polymerase adds nucleotides specifically to the 3′ end of the growing DNA strand, which means DNA synthesis occurs in the 5′ to 3′ direction.
3. Step 3: Know that DNA polymerase has proofreading ability through its exonuclease activity, which allows it to remove incorrectly paired nucleotides and correct errors during replication.
4. Step 4: Differentiate DNA polymerase functions from other enzymes involved in replication, such as helicase (which unwinds DNA), primase (which lays down RNA primers), and ligase (which seals nicks between Okazaki fragments).
5. Step 5: Conclude that the two key functions of DNA polymerase during replication are synthesizing new DNA by adding nucleotides to the 3′ end and proofreading/correcting mismatched bases using exonuclease activity.