미스매치 복구

Following proofreading, errors in DNA replication like pairing adenine with cytosine can persist and maybe fixed through a mechanism called mismatch repair.

In this process, mispaired bases are identified due to their abnormal structure by a mismatch repair protein, such as MutS. Other mismatch repair proteins like MutL then identify the new strand so that the strand with the error is repaired while the template strand remains unchanged.

How the new strand is identified depends on the organism. In E. coli specific DNA sequences are methylated, have a methyl group added, sometime after DNA has been synthesized. E. coli mismatch repair proteins detect the sequences that haven't been methylated yet, identifying the new strand.

In Eukaryotes the new strand is more likely to have nicks, small breaks than the template. Eukaryotic mismatch repair proteins identify the nicked strand and target it for repair.

Once the new strand is identified, the region with the air is cut out by Exonucleuase enzymes, which remove nucleotides.  Finally, DNA Polymerase adds in the correct nucleotides and DNA Ligase seals the gaps at the edges, repairing the error.