Which DNA polymerase is the main replicative enzyme in bacteria?

• A. DNA polymerase I
• B. DNA polymerase II
• C. DNA polymerase III
• D. DNA polymerase V

Answer: (C)

DNA replication in bacteria is driven mainly by DNA polymerase III because it has high processivity and works as the primary replicative enzyme on both the leading and lagging strands. As part of the Pol III holoenzyme, it stays attached to DNA for long stretches thanks to the sliding clamp, allowing rapid and continuous DNA synthesis. Its partners coordinate the two strands and ensure efficient replication across the entire genome. Other polymerases have specialized roles: DNA polymerase I mainly removes RNA primers and fills in gaps after replication, but it is slower and less suited for bulk replication. DNA polymerase II is primarily involved in repair, and DNA polymerase V participates in translesion synthesis during SOS responses, which is error-prone and not the standard copying mechanism. This combination makes DNA polymerase III the correct answer.