Exon-specific Gene Correction (conversion) During Short Evolutionary Periods: Homogenization in a Two-gene Family Encoding the Beta-chain Constant Region of the T-lymphocyte Antigen Receptor

The two genes encoding the beta-chain constant region of the T-lymphocyte antigen receptor appear to have undergone gene conversion in a number of species, including wild and laboratory mice. To examine the frequency of such events during short evolutionary periods, we have characterized the corresponding genes from an African pygmy mouse, Mus minutoides. Sequence analysis indicates that exon 1 regions from these genes have undergone conversion events independent of those observed in other mouse species. Furthermore, the conversion events in all murine species are limited to exon 1 sequences. One such event involves the insertion and subsequent transfer of an entire codon between the two genes. Comparisons with other murine C beta sequences suggest that gene conversion has occurred on the order of every 0.3 Myr during the evolution of a family consisting of only two genes.