Which DNA polymerase purely functions in replication?

Which DNA polymerase purely functions in replication?

• A. DNA polymerase I
• B. DNA ligase
• C. RNA polymerase
• D. DNA polymerase III

Answer: (D)

The enzyme that does the bulk of DNA synthesis during replication is DNA polymerase III. It is highly processive and works on both the leading and lagging strands by adding nucleotides in the 5' to 3' direction, staying tied to the template as replication unfolds. On the lagging strand, it makes short fragments that are later joined, while the RNA primers are eventually removed and replaced by another enzyme. DNA polymerase I also participates in replication, but its main role is primer removal and repair, not continuous synthesis, so it isn’t the purely replication-focused polymerase. RNA polymerase copies RNA for transcription, not DNA, and DNA ligase seals nicks after synthesis rather than building new DNA. So DNA polymerase III is the one that purely functions in replication.

The enzyme that does the bulk of DNA synthesis during replication is DNA polymerase III. It is highly processive and works on both the leading and lagging strands by adding nucleotides in the 5' to 3' direction, staying tied to the template as replication unfolds. On the lagging strand, it makes short fragments that are later joined, while the RNA primers are eventually removed and replaced by another enzyme. DNA polymerase I also participates in replication, but its main role is primer removal and repair, not continuous synthesis, so it isn’t the purely replication-focused polymerase. RNA polymerase copies RNA for transcription, not DNA, and DNA ligase seals nicks after synthesis rather than building new DNA. So DNA polymerase III is the one that purely functions in replication.