<p>Mismatch repair is one of five major DNA repair pathways, the others being homologous recombination repair, non-homologous end joining, nucleotide excision repair, and base excision repair. The mismatch repair system recognises and repairs mispaired or unpaired nucleotides that result from errors in DNA replication. Many proteins involved in the different repair processes also play a role in apoptosis when DNA damage is excessive, thereby helping to prevent carcinogenesis [<cite idref="PUB00014543"/>]. The mismatch repair protein, Mlh1 (mutL homologue 1), has a dual role in DNA repair and apoptosis. Mlh1 acts as a heterodimer in conjunction with Pms2, Pms1 (post-meiotic segregation 1 and 2) or Mlh3 (MutL homologue 3), which function as adaptor proteins that link Msh (MutS homologue) heterodimers to the DNA repair machinery, resulting in excision and repair of the mispaired base [<cite idref="PUB00014545"/>].</p><p> This entry represents the mismatch repair protein MutL. </p>