Mismatch repair and homeologous recombination

•DNA mismatch repair inhibits recombination between slightly diverged DNA sequences.•Evidence for mismatch repair-dependent antirecombination is reviewed.•Mechanistic details of heteroduplex rejection are discussed. DNA mismatch repair influences the outcome of recombination events between diverging DNA sequences. Here we discuss how mismatch repair proteins are active in different homologous recombination subpathways and specific reaction steps, resulting in differential modulation of these recombination events, with a focus on the mechanism of heteroduplex rejection during the inhibition of recombination between slightly diverged (homeologous) DNA sequences.