Mutations in the MLH1 and MSH2 genes result in defective MMR pathways, allowing replication errors to persist. This accumulation of genetic errors can lead to microsatellite instability (MSI), a condition characterized by the expansion or contraction of short tandem repeats in DNA. High levels of MSI are a hallmark of Lynch syndrome and are associated with a higher risk of developing colorectal, endometrial, and other cancers.
