Biased Gene Conversion and its Impact on Human Genome Evolution

Nicolas Galtier, Université Montpellier, Montpellier, France
Laurent Duret, Université Lyon, Villeurbanne, France

Published online: March 2008

DOI: 10.1002/9780470015902.a0020834

Gene conversion between the maternal and paternal alleles occurs during meiosis as part of the complex molecular process of homologous recombination. Consequently, the transmission of alleles can be non-Mendelian for loci located near recombination initiation sites. A large body of evidence suggests that such events of meiotic gene conversion are GC-biased: AT/GC heterozygotes produce an elevated proportion of GC gametes, resulting in an evolutionary advantage for GC over AT alleles. This neutral biased gene conversion (BGC) process has surprisingly strong consequences on the evolution of genomic landscapes in human.

Keywords: recombination; GC-content; isochores; substitution rate; DNA repair

Figure 1. The mechanism of biased gene conversion. During meiotic recombination (a), the plus and minus strands of homologous chromosomes form a heteroduplex (b), which results in DNA mismatches in case of heterozygosity (c). Mismatches are repaired into either G:C (d) or A:T (d¢), resulting in non-Mendelian transmission of alleles. If the repair process is biased towards GC, then the gamete pool becomes GC-enriched.
Figure 2. Relationship between chromosome length, recombination rate and GC-content in chicken. Blue: autosomes; red: sex chromosomes. The Z chromosome (that recombines only in males) and the W chromosome (that does not recombine at all) have a reduced GC-content compared to autosomes of comparable length. Correlation coefficients are given for autosomes. Chromosome length and crossover rate are in Log scale. As expected, GC-content and crossover rates are strongly positively correlated (R2=0.81).
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Related Sub-Topics:

Evolutionary Genomics | Molecular Evolution | Human Evolution
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Article Title: Biased Gene Conversion and its Impact on Human Genome Evolution
 
How to Cite close
Galtier, Nicolas, and Duret, Laurent(Mar 2008) Biased Gene Conversion and its Impact on Human Genome Evolution. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0020834]