Journal of Molecular Evolution

, Volume 41, Issue 2, pp 115–119

Gene conversion vs point mutation in generating variability at the antigen recognition site of major histocompatibility complex loci

  • Tomoko Ohta


In order to assess the roles of gene conversion followed by natural selection and balancing selection for point mutations in polymorphisms at major histocompatibility complex (MHC) loci, DNA sequences of several mammalian taxa were analyzed. Synonymous and nonsynonymous diversities were estimated separately for the antigen recognition site (ARS) and the remaining region of class I and class II genes. In some sequence pairs, the number of nonsynonymous substitutions exceeds that of synonymous substitutions at the ARS. This result indicates that some kind of balancing selection for point mutation is operating. In other sequence pairs (particularly of bovine and of rabbit), the number of synonymous substitutions at the ARS exceeds the same number at the remaining region. This result indicates that gene conversion involving a short region followed by natural selection is important. In general, a combination of gene conversion, point mutation, natural selection and random drift is thought to have contributed to polymorphisms.

Key words

Hypervariability at the ARS of MHC loci Selection Gene conversion 


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Copyright information

© Springer-Verlag New York Inc 1995

Authors and Affiliations

  • Tomoko Ohta
    • 1
  1. 1.National Institute of GeneticsMishimaJapan

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