The orangutan adult alpha-globin gene locus: duplicated functional genes and a newly detected member of the primate alpha-globin gene family.

We have cloned and sequenced the complete alpha 1- and alpha 2-globin genes of the orangutan, and here we compare them to the homologous genes of the human. The pattern of similarity apparent among the genes is most consistent with a model of gene correction operating on the primate alpha-globin cluster. This correction breaks down in both human and orangutan in the 3'-untranslated region at 14 base pairs downstream from the termination codon. The unit evolutionary period values calculated for either the replacement substitution or the silent substitutions are only slightly higher than the previously established molecular clock predicts. The 7-base-pair insertion in intron 2 of the human alpha 1-globin gene is not present in either orangutan gene, suggesting that this insertion is not the cause of the sequence divergence in the 3'-untranslated regions of primate alpha 2- and alpha 1-globin genes. Finally, blotting hybridization and partial DNA sequencing reveal a newly detected member of the primate alpha-globin gene family, which is located downstream from the duplicated adult alpha-globin genes.