5th March 2024

DNA mismatch repair

Mismatch repair systems exist within all cells to help correct errors made during DNA replication by DNA polymerase. Mutation in the genes responsible for this system results in microsatellite instability. Microsatellites are short repeat tandem sequences within the gene that can obtain fewer or extra repeats during DNA replication. Instability occurs when the mismatch repair mechanism fails, resulting in additional nucleotides being added to the strand and can result in frameshift mutations that inactivate the gene. This is most commonly associated with colorectal, stomach and endometrial cancers.

HNPCC or Lynch syndrome is the most common example of inheritable cancer caused by microsatellite instability resulting from mutations in the MSH2 or MLH1 genes.