The sequence of the gorilla fetal globin genes: Evidence for multiple gene conversions in human evolution

A. F. Scott, P. Heath, S. Trusko, S. H. Boyer, W. Prass, M. Goodman, J. Czelusniak, L. Y. Chang, J. L. Slightom

Research output: Contribution to journalArticle

Abstract

Two fetal globins ((G)γ and (A)γ) from one chromosome of a lowland gorilla (Gorilla gorilla gorilla) have been sequenced and compared to three human loci (a (G)γ-gene and two (A)γ-alleles). A comparison of regions of local homology among these five sequences indicates that long after after the duplication that produced the two nonallelic γ-globin loci of catarrhine primates, about 35 million years (Myr) ago, at least one gene conversion event occurred between these loci. This conversion occurred not long before the ancestral divergence (about 6 Myr ago) of Homo and Gorilla. After this ancestral divergence, a minimum of three more gene conversion events occurred in the human lineage. Each human (A)γ-allele shares specific sequence features with the gorilla (A)γ-gene: one such distinctive allelic feature involves the simple repeated sequence in IVS 2. This suggests that early in the human lineage the (A)γ-genes may have undergone a crossing-over event mediated by this simple repeated sequence. The DNA sequences from coding regions of both (G)γ- and (A)γ-loci, a comparison of 292 codons in the corresponding gorilla and human genes, show an unusually low evolutionary rate, with only two nonsilent differences and, surprisingly, not even one silent substitution. The two nonsynonymous substitutions observed predict a glycine at codon 73 and an arginine at codon 104 in the gorilla (A)γ-sequence rather than aspartic acid and lysine, respectively, in human (A)γ. Because only arginine has been found at position 104 in γ-chains of Old World monkeys, it may represent the ancestral residue lost in gorilla and human (G)γ-chains and in the human (A)γ-chain. Possibly the arginine codon (AGG) was replaced by the lysine codon (AGG) in the (G)γ-gene of a common ancestor of Home and Gorilla and then was transferred to the (A)γ-gene by subsequent conversions in the human lineage. DNA sequence conversions, similar to that attributed to the fetal γ-globin genes, appear to be relatively frequent phenomena and, if widespread throughout the genome, may have profound evolutionary consequences.

Original languageEnglish (US)
Pages (from-to)371-389
Number of pages19
JournalMolecular biology and evolution
Volume1
Issue number5
StatePublished - 1984

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Genetics

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    Scott, A. F., Heath, P., Trusko, S., Boyer, S. H., Prass, W., Goodman, M., Czelusniak, J., Chang, L. Y., & Slightom, J. L. (1984). The sequence of the gorilla fetal globin genes: Evidence for multiple gene conversions in human evolution. Molecular biology and evolution, 1(5), 371-389.