Thus, testosterone leads to the development of the internal genitalia and dihydrotestosterone leads to the development of the external genitalia see Figures 3—13—2and 3—3. After 20 weeks of gestation, Leydig cells involute, and circulating testosterone levels decrease progressively to levels observed in female fetuses.
Similarly, in individuals who reached the age of 85 had, on average, another 4 years of life, with very little difference between the sexes. Genes Cells.
Recent findings suggest that most probably the coordinated action of several factors is needed for the differentiation and stabilization of the ovaries - Table 3Figs. Cytochrome b5 is required for optimal 17,20 lyase activity Physiological Reviews. Paris
WNT-4, a vertebrate homologue of the D. Significant differences among females occur if the fetus is located between two males or with a male on one side or with no male on either side. The critical role of the Y chromosome and of atypical prenatal sex differentiation and development in Caloundra hormones in male orientation is well documented, the development of the female sexual differentiation occurring in the absence of male genetic determinants.
Homeoproteins Six1 and Six4 regulate male sex determination and mouse gonadal development. Researchers should choose models that mirror human sex differences and that are appropriate for the human conditions being addressed. TABLE 7.
Variations in the phenotypic characteristics of the different sexes are determined during development by internal chemical signals. WT1 mutations contribute to abnormal genital system development and hereditary Wilms' tumour. SRY and Dax-1 appear to act antagonistically in gonadal dysgenesis Parker et al.