LAUSR

A detailed cytogenetic study on anurans belonging to the unranked taxon Terraranae revealed the existence of microscopically recognizable XY♂/XX♀ or ZZ♂/ZW♀ sex chromosomes in 11 species. Furthermore, in some species Y-autosome translocations were found, of which 5 could be confirmed. The male individuals carrying the Y-autosome translocations still coexist with the males showing the original karyotypes. The present report gives an overview on the mitotic and meiotic structure, staining and banding properties, functional importance, and similarities and differences of these Y-autosome translocations which are very rare in vertebrates. A mathematical model was constructed that calculates the various probabilities of further chromosome rearrangements in these karyotypes with Y-autosome translocations. The localization of the differential segment containing the hypothetical male sex-determining gene in the Y chromosome is discussed.