During DNA replication, which enzyme performs proofreading to remove errors and replace them?

During DNA replication, which enzyme performs proofreading to remove errors and replace them?

• A. Ligase
• B. Nuclease
• C. RNA Polymerase
• D. DNA Polymerase

Answer: (D)

Proofreading during DNA replication is performed by DNA polymerase, which has a 3' to 5' exonuclease activity. As the polymerase adds nucleotides, it checks that each base pairs correctly. If a mismatch slips in, the enzyme backs up and excises the incorrect nucleotide from the growing strand, creating a new correct 3' end. It then resumes synthesis, inserting the proper nucleotide and continuing along the template. This built-in proofreading greatly reduces replication errors. The other options don’t perform this immediate, base-by-base correction: ligase seals nicks after synthesis, RNA polymerase is responsible for creating RNA primers, and nucleases can cut nucleic acids but aren’t the specialized proofreading function during replication.

Proofreading during DNA replication is performed by DNA polymerase, which has a 3' to 5' exonuclease activity. As the polymerase adds nucleotides, it checks that each base pairs correctly. If a mismatch slips in, the enzyme backs up and excises the incorrect nucleotide from the growing strand, creating a new correct 3' end. It then resumes synthesis, inserting the proper nucleotide and continuing along the template. This built-in proofreading greatly reduces replication errors. The other options don’t perform this immediate, base-by-base correction: ligase seals nicks after synthesis, RNA polymerase is responsible for creating RNA primers, and nucleases can cut nucleic acids but aren’t the specialized proofreading function during replication.