sentences:  DNA mismatches occur where one base is improperly paired with another base, or where there is a short addition or deletion in one strand of DNA that is not matched in the other strand.Mismatches commonly occur as a result of DNA replication errors or during genetic recombination.Recognizing those mismatches and repairing them is important for cells because failure to do so results in microsatellite instability] and an elevated spontaneous mutation rate (mutator phenotype).