One of two growth hormone genes in coho salmon is sex-linked

Stephen H. Forbes, Kathy L. Knudsen, Thomas W. North, Fred W. Allendorf

Research output: Contribution to journalArticlepeer-review

78 Scopus citations


Salmonid fishes have two growth hormone genes resulting from their polyploid ancestry. We used the polymerase chain reaction to examine genetic variation in the third intron (C) of both of these genes in coho salmon (Oncorhynchus kisutch). A polymorphism in the length of intron C in GH-1 is due to a variable number of copies of a 31-nt repeat that is absent from GH- 1 of the closely related chinook salmon (Oncorhynchus tshawytscha) and rainbow trout (Oncorhynchus mykiss). Thus, this tandem repeat sequence has become established in the genome of coho salmon since the separation of this species from its closest relatives. All male coho salmon examined have an allele at the second growth hormone gene, GH-2, that is not found in females. GH-2 is thus on the sex chromosome and there is no recombination between GH- 2 and the sex-determining locus (SEX). Sequences of intron C indicate much greater divergence between the X chromosome-specific allele and the Y chromosome-specific allele within coho salmon than between the X chromosome- specific alleles of coho and the closely related chinook salmon. Thus, absence of recombination between GH-2 and SEX apparently predates separation of these two species.

Original languageEnglish (US)
Pages (from-to)1628-1631
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number5
StatePublished - Mar 1 1994
Externally publishedYes


  • evolution
  • intron
  • Oncorhynchus
  • recombination
  • sex chromosome

ASJC Scopus subject areas

  • General
  • Genetics


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