Gene Conversion

Gene conversion is an event in which a portion of the sequence of one chromosome is altered to form a copy of another homologous sequence. Conversion occurs as a result of mismatch repair of double-strand breaks during recombination (and thus is common at recombination hotspots), in which genetic information is copied from an intact sequence to the region of recombination that contains a double-strand break. Gene conversion is typically biased toward AT→GC conversion events, and this biased gene conversion is thought to be responsible for human accelerated regions. Human chromosome Y has multiple palindromic sequences in which gene conversion has resulted in nearly identical gene sequences within the palindromes. The process, in conjunction with comparable events occurring in the chimpanzee lineage, has led to increased sequence divergence between orthologous loci on chromosome Y in these two species, and similar events have been seen among humans and non-human primates that have increased the divergence in sequence between species. Multiple gene families in humans have also been altered by gene conversion events, including the polycystic kidney disease I family, olfactory receptor family and SIGLEC family.