Laurent DURET – Biased Gene Conversion : the dark side of recombination

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Date(s) - 6 avril 2016

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Recombination is typically thought as a symmetrical process resulting in large-scale reciprocal genetic exchanges between homologous chromosomes. Recombination events, however, are also accompanied by short-scale, unidirectional exchanges in the neighborhood of the initiating double-strand break : gene conversion. A large body of evidence suggests that gene conversion is GC-biased in mammals. AT/GC heterozygotes produce a larger amount of GC- than AT-gametes, thus conferring a population advantage to GC-alleles in high-recombining regions. This apparently unimportant feature of our molecular machinery has strong evolutionary consequences. Structurally, GC-biased gene conversion (gBGC) explains the spatial distribution of GC-content in mammalian genomes – the so-called isochore structure. Functionally, gBGC promotes the “undesired” segregation and fixation of deleterious AT->GC mutations, thus increasing our genomic mutation load. I will present an analysis of the signatures of gBGC in the tree of life. Our results show that gBGC is probably a universal process, present not only in many eukaryotic taxa but also in bacteria. Laurent DURE [