Common spontaneous sex-reversed XX males of the medaka Oryzias latipes.
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.
Nanda
Indrajit
I
Institute for Human Genetics, Biocenter, University of Würzburg, D-97074 Würzburg, Germany.
Hornung
Ute
U
Kondo
Mariko
M
Schmid
Michael
M
Schartl
Manfred
M
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