Which enzyme synthesizes a new DNA strand by adding nucleotides to the template during replication?

Which enzyme synthesizes a new DNA strand by adding nucleotides to the template during replication?

• A. Ligase
• B. DNA polymerase
• C. Helicase
• D. Topoisomerase

Answer: (B)

DNA replication relies on an enzyme that builds a new strand by adding nucleotides that pair with the template strand. DNA polymerase is the enzyme that does this synthesis. It adds nucleotides to the growing 3' end of the new strand, extending in the 5' to 3' direction and using the template strand to guide correct base pairing. Many DNA polymerases also have proofreading activity to correct mistakes. A primer is needed to start synthesis, provided by primase as a short RNA sequence. Other enzymes have different roles: helicase unwinds the double helix, topoisomerase relieves torsional strain ahead of the fork, and ligase seals gaps between Okazaki fragments on the lagging strand.

DNA replication relies on an enzyme that builds a new strand by adding nucleotides that pair with the template strand. DNA polymerase is the enzyme that does this synthesis. It adds nucleotides to the growing 3' end of the new strand, extending in the 5' to 3' direction and using the template strand to guide correct base pairing. Many DNA polymerases also have proofreading activity to correct mistakes. A primer is needed to start synthesis, provided by primase as a short RNA sequence. Other enzymes have different roles: helicase unwinds the double helix, topoisomerase relieves torsional strain ahead of the fork, and ligase seals gaps between Okazaki fragments on the lagging strand.