Analysis of information sources in references of the Wikipedia article "Žena" in Croatian language version.
All human individuals—whether they have an XX, an XY, or an atypical sex chromosome combination—begin development from the same starting point. During early development the gonads of the fetus remain undifferentiated; that is, all fetal genitalia are the same and are phenotypically female. After approximately 6 to 7 weeks of gestation, however, the expression of a gene on the Y chromosome induces changes that result in the development of the testes. Thus, this gene is singularly important in inducing testis development. The production of testosterone at about 9 weeks of gestation results in the development of the reproductive tract and the masculinization (the normal development of male sex characteristics) of the brain and genitalia. In contrast to the role of the fetal testis in differentiation of a male genital tract and external genitalia in utero, fetal ovarian secretions are not required for female sex differentiation.
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