Journal of Heredity Advance Access published online on May 25, 2008
Journal of Heredity, doi:10.1093/jhered/esn038
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Characterization of a Chromosomal Rearrangement Responsible for Producing "Apparent" XY-Female Fall-Run Chinook Salmon in California
From the National Marine Fisheries Service, Northwest Fisheries Science Center, Conservation Biology Division, 2725 Montlake Boulevard East, Seattle, WA 98112 (Williamson); the School of Biological Sciences, Washington State University, 14204 NE Salmon Creek Avenue, Vancouver, WA 98686 (Phillips); and the Genomic Variation Laboratory, Department of Animal Science, University of California, Davis, One Shields Avenue, Davis, CA 95616 (May)
Address correspondence to K.S. Williamson at the address above, or e-mail: Kevin.williamson{at}noaa.gov.
Fluorescence in situ hybridization (FISH) was used to identify the X and Y chromosomes of offspring produced by normal and "apparent" XY-female fall-run Chinook salmon (Oncorhynchus tshawytscha) from California. FISH experiments were performed using probes to 2 sex-linked loci, growth hormone pseudogene (GH-
), and OtY1, as well as a probe to a sex-linked microsatellite (Omy7INRA). Comparison of FISH staining patterns between the offspring produced by normal and apparent XY-females revealed that the apparent XY-female examined transmitted a "Y-like" chromosome with an attenuated OtY1 and GH-
signal to half of its offspring. Segregation analysis of microsatellites derived from rainbow trout (Oncorhynchus mykiss) with respect to phenotypic sex was carried out for 2 normal and 2 apparent XY-female Chinook salmon families. Inheritance patterns of Omy7INRA were consistent with this locus being closely linked to GH-
in males and in apparent XY-females carrying the Y-like chromosome. Another microsatellite locus (Omm1077) was closely linked to the primary sex-determining locus (SEX) in males but not to GH-
/OtY1 in apparent XY-females. The FISH analyses suggest that apparent XY-female fall-run Chinook salmon in California are not the product of a Y chromosome to autosome translocation. Despite the combined FISH and inheritance analyses, we were unable to differentiate between 2 alternative explanations for apparent XY-females, namely, recombination of markers between the sex chromosomes, or a Y chromosome with a dysfunctional or missing sex-determining region.
Corresponding Editor: Bill Modi
Received March 30, 2007
Accepted April 16, 2008