Concerted evolution of the primate immunoglobulin alpha-gene through gene conversion.

We determined four nucleotide sequences of the hominoid immunoglobulin alpha (C alpha) genes (chimpanzee C alpha 2, gorilla C alpha 2, and gibbon C alpha 1 and C alpha 2 genes), which made possible the examination of gene conversions in all hominoid C alpha genes. The following three methods were used to detect gene conversions: 1) phenetic tree construction; 2) detection of a DNA segment with extremely low variability between duplicated C alpha genes; and 3) a site by site search of shared nucleotide changes between duplicated C alpha genes. Results obtained from method 1 indicated a concerted evolution of the duplicated C alpha genes in the human, chimpanzee, gorilla, and gibbon lineages, while results obtained from method 2 suggested gene conversions in the human, gorilla, and gibbon C alpha genes. With method 3 we identified clusters of shared nucleotide changes between duplicated C alpha genes in human, chimpanzee, gorilla, and gibbon lineages, and in their hypothetical ancestors. In the present study converted regions were identified over the entire C alpha gene region excluding a few sites in the coding region which have escaped from gene conversion. This indicates that gene conversion is a general phenomenon in evolution, that can be clearly observed in non-functional regions.