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)