title: Alteration of the sex determining system resulting from structural change of the sex chromosomes in the frog Rana rugosa.
abstract: Rana rugosa in Japan is divided into four geographical races on the basis of the karyotype of the sex chromosomes: one in which heteromorphic sex chromosomes occur in the female sex (ZW/ZZ-system), another in which they are present in males (XX/XY-system), and the remaining two in which no heteromorphism is seen in either sex. The last two inherit the XX/XY sex determining system. Y and Z chromosomes in the former two are of the same karyotype as the no. 7 chromosomes seen in one of the latter two, whereas X and W are caused by two inversions that occurred in the original Xs (no. 7). In this study, we first attempted to detect the structural difference between the resulting X and W by examining their chiasma formation. The chiasma distribution between X and W was closely similar to that between two Xs, suggesting that the W and X are identical in structure. Regarding the change from XX/XY- to ZW/ZZ-system, the simplest explanation is that the putative female-determining gene(s) on the W grew functionally stronger by inversions. Next, we examined the sex of triploids having two Xs and one Z. The data showed that the triploids with two original Xs and a Z were all male, whereas most of those with two resulting Xs and a Z developed into females as expected. We speculated that the female-determining gene(s) on the resulting X grew mildly stronger functionally by position effect, whereas those on the W grew much stronger for some other reason (e.g., duplication). J. Exp. Zool. 286:313-319, 2000.
authors.affiliation: Laboratory for Amphibian Biology, Faculty of Science, Hiroshima University, Higashihiroshima 739-8526, Japan. hotani@ipc.hiroshima-u.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Ohtani
authors.forename: I
authors.initials: I
authors.lastname: Miura
authors.forename: H
authors.initials: H
authors.lastname: Hanada
authors.forename: Y
authors.initials: Y
authors.lastname: Ichikawa
mesh_terms: D000818:Animals; D003433:Crosses, Genetic; D005260:Female; D015321:Gene Rearrangement; D008297:Male; D008675:Metamorphosis, Biological; D010053:Ovary / Q000166:cytology; D011123:Polyploidy; D011898:Ranidae / Q000235:genetics*; D012730:Sex Chromosomes / Q000235:genetics*; D019849:Sex Determination Processes; D012744:Sex Ratio; D013737:Testis / Q000166:cytology