The Chromosomal Basis of Sex Differentiation in Marsupials

摘要: Data on ten intersexual marsupials, eight of which were known karyotype, are presented and reviewed. Three the intersexes or suspected XO/XX XO/XX/XXX, two XXY, one was XXY/XY/XX XY in sex chromosome constitution. In all three had an XO cell line, but no Y found any cell, a small empty scrotum to side midline midline. Those non-midline mammary tissue opposite partial complete pouch. The intersex with pouch glands. Unilateral bilateral putative spermatic cords, not containing ductus deferens, descended scrotum, other respects internal reproductive systems like those normal XX female marsupials. Intersexes body size when adult. XXY pouches glands none scrotum. All well developed male undescended testis-like gonads, intermediate size. Both also glands, male-type testes except for absence post- primary spermatocyte stages spermatogenesis. One fully adult it did differ from males same species measurements, weight secondary coloration. unknown constitution, morphologically XO/XX/XXX mosaic centrally placed other, essentially comparable intersexes. data interpreted, at whole level, as follows. presence single active X scrotal cord development initiated, whereas they inhibited chromosomes. Complete completely inhibited, unilateral partly gland development. responsible gonadal and, apparently through production MIS, eliminated Miillerian (i.e. female) ducts. Development type system dependent apparently, androgen gonads. At gene level may be interpreted terms hypothetical S 'switch' locus, carried chromosome, induced dose double dose. If this hypothesis is correct, would explain occurrence incomplete X-chromosome inactivation marsupials; X-inactivation impossible marsupials because leave each