Slightom J L, Theisen T W, Koop B F, Goodman M
J Biol Chem. 1987 Jun 5;262(16):7472-83.
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.
我们已经确定了来自一只猩猩（婆罗洲猩猩）单一染色体上相连的γ1和γ2胎儿珠蛋白基因的核苷酸序列，并将它们与其他猿猴灵长类动物的相应基因（人类、黑猩猩、大猩猩的γ1和γ2基因，以及蜘蛛猴的单一γ基因）进行了比较。先前的研究表明，狭鼻猿灵长类动物中的两个γ基因位点是大约2500万至3500万年前一次基因复制的结果。然而，对排列好的γ基因序列的比较显示，这些基因包含三个具有不同进化历史的区域，其中只有3'端的三分之一清楚地反映了γ基因复制所预期的祖先性质。为了解释这些不同的进化历史以及人类的亲缘关系，我们提供了序列转换发生的证据，这种转换影响所有人类物种的区域1（从5'侧翼120个碱基对到外显子2），并不同程度地延伸到区域2（从内含子2到外显子3）。对所提出的转换的仔细研究进一步表明，所确定的13次转换中有12次涉及γ1转换γ2。这些转换的极性可能是这些基因之间差异存活的结果，因为在人类胎儿发育过程中，γ1基因比γ2基因优先表达，并且它可能受到更大的选择压力以保持不变。
