Biased gene conversion and the evolution of mammalian genomic landscapes

Annu Rev Genomics Hum Genet. 2009;10:285-311. doi: 10.1146/annurev-genom-082908-150001.


Recombination is typically thought of 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 known as gene conversion in the neighborhood of the initiating double-strand break. A large body of evidence suggests that gene conversion is GC-biased in many eukaryotes, including mammals and human. AT/GC heterozygotes produce more 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 major evolutionary consequences. Structurally, GC-biased gene conversion explains the spatial distribution of GC-content in mammalian genomes-the so-called isochore structure. Functionally, GC-biased gene conversion promotes the segregation and fixation of deleterious AT --> GC mutations, thus increasing our genomic mutation load. Here we review the recent evidence for a GC-biased gene conversion process in mammals, and its consequences for genomic landscapes, molecular evolution, and human functional genomics.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Base Composition
  • Evolution, Molecular*
  • Gene Conversion*
  • Genome*
  • Humans
  • Mammals / genetics*
  • Selection, Genetic