sentences:  It functions exclusively when bound to hMSH2 as a heterodimer, although hMSH2 itself can function as a homomultimer or as a heterodimer with hMSH3.Mismatches commonly occur as a result of DNA replication errors, genetic recombination, or other chemical and physical factors.Recognizing those mismatches and repairing them is extremely important for cells, because failure to do so results in microsatellite instability, an elevated spontaneous mutation rate (mutator phenotype), and susceptibility to HNPCC.