The ZW sex-determination system is reversed compared to the XY system: The sex of an early embryo cannot be determined because the reproductive structures do not differentiate until the seventh week. This includes both internal and external genetic sex differentiation differentiation.
Sexual differentiation in humans
Some fish have variants of the XY sex-determination systemas well as the regular system. Dihydrotestosterone will differentiate the remaining male characteristics of the external genitalia. Phenotypic sex refers to the structures of the external and internal genitalia.
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The development of sexual differences begins with the XY sex-determination system that is present in humans, and complex mechanisms are responsible for the development of the phenotypic differences between male and female humans from an undifferentiated zygote. Articles with short description All articles with unsourced statements Articles with unsourced statements from September Wikipedia articles needing genetic sex differentiation from January Articles with unsourced statements from January Use dmy dates from May genetic sex Development of the gonads Differentiation ridge Pronephric duct Mesonephric duct Paramesonephric duct Vaginal plate Definitive urogenital sinus. In some diseases and circumstances, other androgens may be present in high enough concentrations to cause partial or rarely complete masculinization of the external genitalia of a genetically female fetus.