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Immunol Rev. 1999 Feb;167:319-25.

Effect of gene conversion on polymorphic patterns at major histocompatibility complex loci.

Author information

1
Department of Population Genetics, National Institute of Genetics, Mishima, Japan. tohta@lab.nig.ac.jp

Abstract

The pattern of polymorphisms at MHC loci was studied by computer simulations and by DNA sequence analyses, with special reference to synonymous and non-synonymous divergence among alleles. A model of overdominance plus short-term selection was simulated for a gene family with allelic and non-allelic gene conversion. It was found that the ratio of non-synonymous-to-synonymous divergence among alleles decreases as the non-allelic conversion becomes more frequent. On the other hand, the ratio of synonymous divergence at the antigen recognition site to that at non-coding region increases by non-allelic conversion. By comparing such a pattern with the observed values of mammalian genes, it is suggested that non-allelic conversion is less frequent in human genes than in genes of other mammals. A quantitative analysis on the patchwork pattern was attempted by using identity excess among nucleotide sites of a gene. Comparison of simulation results with DNA data analysis shows that the rate of allelic conversion is high.

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