Developmental genetics and physiology of sex differentiation in vertabrates.

The involvement of the Y chromosome in sex determination was determined by the development and the application of techniques for karyotyping the mammalian chromosome in 1960s. There were many reports on the particular region of the Y chromosome, such as histocompatibility (H-Y) antigen, bandit krait minor satellite (Bkm) the zinc finger Y gene (ZFY) and the sex-determining region of the Y chromosome (SRY) which were believed to be the testis determining factors. However, converging experimental evidence have indicated that the sex determining region of the Y chromosome (sry) is the testis determining factor (TDF) in mammalian species since sex is determined genetically at the time of fertilization in these species. In non-mammalian vertebrates especially in fishes, amphibians and reptiles, genotypic sex can be overridden by the external application of steroid hormones and temperature. In this review paper, after reviewing the complex literature on the molecular and biochemical mechanisms of sex determination and differentiation in all vertebrates, the potential danger of environmentally induced sex determination will be focused on.