Structure and organization of the bovine β-globin genes

Abstract

Genomic clones spanning the entire cow β-globin gene locus have been isolated and characterized. The clones demonstrate that the linkage of embryonic-like (ε) genes and pseudogenes (ψ) to the previously described fetal (γ) and adult (β) genes is as follows: 5'-ε3-ε4-ψ3-β-ε1-ε2-ψ1-ψ2-γ-3'. Present data indicate that, like that of the goat, the fetal and adult genes arose via block duplication of an ancestral four-gene set: ε-ε-ψ-β. This duplication event preceded the divergence of cows and goats, which occurred ≥18-20 Myr ago. However, cows do not have the additional four-gene block containing a preadult/stress globin gene (β(c)). Furthermore, the cow fetal cluster contains an extra β-like pseudogene, which apparently arose by a smallscale duplication. The fixation of this duplication may indicate a possible evolutionary role for pseudogenes.