Gene evolution in the chicken beta-globin cluster.

We have determined the cDNA sequence of the chicken embryonic beta-like epsilon-globin gene. Comparison with the sequences of the chicken rho-globin and beta-globin genes reveals the presence of two regions that are identical or nearly identical in epsilon and rho. The first contains the 5' untranslated sequence and exon 1, while the second region includes the second half of exon 2. Outside these regions rho and epsilon are less homologous to each other than to the adult beta-globin gene. The embryonic rho and epsilon genes are located at opposite ends of the beta-globin-gene cluster, not contiguously as are all other known pairs of simultaneously expressed globin genes. We suggest a role for gene conversion in the synchronization of expression of two highly diverged genes.