Practice question

SRY gene on Y chromosome encodes testis-determining factor transcription factor initiating male cascade. SRY upregulates SOX9 via SF1 synergy in bipotential gonad, driving Sertoli differentiation, AMH secretion and Leydig testosterone synthesis promoting Wolffian development and testis morphogenesis. In XX individuals lacking SRY, absence of SOX9 upregulation allows ovarian pathway via WNT4, RSPO1, FOXL2 activation leading to granulosa differentiation and ovary formation. Thus default or more accurately alternative WNT-driven pathway yields ovary when SRY absent. Absence does not cause testis, hermaphroditism or absolute sterility per se but leads to female differentiation; secondary infertility factors depend on karyotype.