During DNA replication, which enzyme is responsible for proofreading the newly synthesized strand?

The enzyme responsible for proofreading the newly synthesized strand during DNA replication is polymerase. Specifically, DNA polymerases have a built-in proofreading ability that allows them to check the newly added nucleotides against the template strand.

As DNA polymerase adds nucleotides to a growing DNA strand, it can detect any mismatches or incorrect base pairing. If an error is identified, the enzyme can remove the incorrect nucleotide through its exonuclease activity and replace it with the correct one. This proofreading function is critical for maintaining the fidelity of DNA replication, ensuring that the genetic information is accurately passed on during cell division.

In contrast, helicase unwinds the DNA double helix, ligase seals gaps between Okazaki fragments on the lagging strand, and primase synthesizes the RNA primer necessary for starting DNA synthesis. These functions, while essential for the overall process of replication, do not involve the proofreading step of correcting errors in the newly synthesized DNA.