title: Common spontaneous sex-reversed XX males of the medaka Oryzias latipes.
abstract: In the medaka, a duplicated version of the dmrt1 gene, dmrt1bY, has been identified as a candidate for the master male sex-determining gene on the Y chromosome. By screening several strains of Northern and Southern medaka we identified a considerable number of males with normal phenotype and uncompromised fertility, but lacking dmrt1bY. The frequency of such males was >10% in some strains and zero in others. Analysis for the presence of other Y-linked markers by FISH analysis, PCR, and phenotype indicated that their genotype is XX. Crossing such males with XX females led to a strong female bias in the offspring and also to a reappearance of XX males in the following generations. This indicated that the candidate male sex-determining gene dmrt1bY may not be necessary for male development in every case, but that its function can be taken over by so far unidentified autosomal modifiers.
authors.affiliation: Institute for Human Genetics, Biocenter, University of Würzburg, D-97074 Würzburg, Germany.
authors.forename: Indrajit
authors.initials: I
authors.lastname: Nanda
authors.forename: Ute
authors.initials: U
authors.lastname: Hornung
authors.forename: Mariko
authors.initials: M
authors.lastname: Kondo
authors.forename: Michael
authors.initials: M
authors.lastname: Schmid
authors.forename: Manfred
authors.initials: M
authors.lastname: Schartl
mesh_terms: D000818:Animals; D005260:Female; D057850:Hermaphroditic Organisms; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D009990:Oryzias / Q000235:genetics* / Q000378:metabolism; D019849:Sex Determination Processes; D014960:X Chromosome