STRUCTURAL AND EVOLUTIONARY ANALYSIS OF THE BOVINE BETA GLOBIN GENES (CLONING, DNA SEQUENCE, COW)

The work presented in this thesis document describes the cloning and molecular characterization of the cow (Bos taurus) beta globin genes. This organism and gene system was chosen in order to address questions concerning the developmental regulation of globins, the possible role of repetitive elements in the regulation of these genes, and the evolutionary processes involved in the formation of this gene family.;Overlapping genomic clones were isolated which contained all the (beta)-like globin genes of the cow. These clones demonstrated the linkage of these genes as follows: (epsilon)('3)-(epsilon)('4)-(psi)('3)-(beta)-(epsilon)('1)-(epsilon)('2)-(psi)('1)-(psi)('2)-(gamma), where (epsilon) represents embryonic-like genes, (psi) as pseudogenes, (gamma) as the fetal gene, and (beta) as the adult gene. This arrangement evolved in part by a block duplication of a primordial 4 gene set, (epsilon)-(epsilon)-(psi)-(beta), to produce two highly analogous clusters. The last (3' most) gene in the primordial set was thus recruited to form two developmentally distinct genes, (gamma) and (beta). In contrast, goats have a triplicated 4 gene set, with the additional cluster possessing the preadult gene. Therefore, the absence of a preadult gene in the cow is simply due to an absence of any such structural gene, not a differential expression of orthologous genes.;DNA sequence analysis of the cloned fetal and adult genes revealed the presence of different Alu-type insertions in their introns. We hypothesized that they inhibited gene conversion, thus allowing the duplicated fetal and adult genes to evolved differentiated function. Two embryonic-like genes, (epsilon)('2) and (epsilon)('4), which do not contain insertions in their introns, have undergone gene conversion since their duplication.;The cow globin family contains a duplicated pseudogene in the fetal gene cluster. This duplication occurred after the block duplication which formed two 4-gene sets. The preservation of this structure indicates a possible evolutionary function for pseudogenes.;Cows exhibit switches from embryonic to fetal to adult forms of hemoglobin during development, while another ruminant, the goat, has an additional switch from fetal to preadult to adult globin.