 Homologous recombination ( HR ) is essential to cell division in eukaryotes like plants , animals , fungi and protists . In cells that divide through mitosis , homologous recombination repairs double @-@ strand breaks in DNA caused by ionizing radiation or DNA @-@ damaging chemicals . Left unrepaired , these double @-@ strand breaks can cause large @-@ scale rearrangement of chromosomes in somatic cells , which can in turn lead to cancer . 
