Paul Modrich: Mechanisms in DNA mismatch repair

Biochemist Paul Modrich was awarded the 2015 Nobel Prize in Chemistry along with Tomas Lindahl and Aziz Sancar "for mechanistic studies of DNA repair." Paul Modrich worked over decades on the idea of decoding the repair mechanism in the DNA code. Just as with all cell mechanisms, chromosome replication is not free from mistakes, misspellings in the genetic code are constantly happening. In 1989, Modrich succeeded in identifying the mismatch repair system (MMR) in cells. By studying bacterial viruses, Paul Modrich showed how methyl groups attached to the DNA molecule act as signals for repairing incorrect replications of DNA. Repair enzymes then cut out the mismatched base and replaces it. Mismatch repair is a mutation avoidance system, if it does not work properly, cancer and other diseases can develop.