What is the role of exonuclease in DNA replication?

Exonucleases can act as proof-readers during DNA polymerization in DNA replication. They work by scanning along the newly synthesized strand directly behind the DNA polymerase. If the last nucleotide added is mismatched, it will be removed by the exonuclease. Therefore, exonucleases can be directly involved in repairing damaged DNA. Some polymerases (such as DNA polymerase I) have the intrinsic exonuclease activity derived from their exonuclease domains, which maintains the fidelity of DNA replication.