Schematic representation of nonallelic homologous recombination by both inter- and intrachromosomal events. The black and grey lines represent the homologous chromosomes. The arrows represent low copy repeats (LCRs). The different tints of the LCRs are used to indicate the position of the cross-over. In (A) they represent the LCR on the two different chromosomes; in (B) they represent either the LCR on the two different sister-chromatids or the two different LCR on a single sister chromatid. The X indicates the site of the cross-over.