Orangutan fetal globin genes. Nucleotide sequence reveal multiple gene conversions during hominid phylogeny.
We have determined the nucleotide sequences of the linked gamma 1- and gamma 2- fetal globin genes from a single orangutan (Pongo pygmaeus) chromosome and compared them with the corresponding genes of other simian primates (gamma 1- and gamma 2-genes of human, chimpanzee, gorilla, and the single gamma-gene of the spider monkey). Previous studies have indicated that the two gamma-gene loci in catarrhine primates resulted from a duplication about 25-35 million years ago. However, comparisons of aligned gamma-gene sequences show that these genes contain three regions with distinct histories of which only the 3' third clearly reflects the ancestral nature expected of the gamma-gene duplication. To explain these different evolutionary histories and also hominid relationships we provide evidence for the occurrence of sequence conversions which affect region 1 (120 base pairs 5'-flanking through exon 2) in all hominid species and extend to varying degrees into region 2 (intron 2 through exon 3). Close examinations of the proposed conversions further suggest that 12 of the 13 conversions identified involved gamma 1 converting gamma 2. Polarity of these conversions may be a result of differential survival between these genes because during human fetal development the gamma 1-gene is preferentially expressed over the gamma 2-gene and it may be subjected to greater selection pressure to remain unaltered.
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D005333:Fetus / Q000378:metabolism*; D005796:Genes; D005914:Globins / Q000235:genetics*; D000882:Haplorhini / Q000235:genetics*; D015186:Hominidae / Q000235:genetics*; D006801:Humans; D010802:Phylogeny; D011148:Pongo pygmaeus / Q000235:genetics*
D005914:Globins; D004262:DNA Restriction Enzymes