When complexed with the SF1 protein, TDF acts as a transcription factor that causes upregulation of other transcription factors, most importantly SOX9.[1] Its expression causes the development of primary sex cords, which later develop into seminiferous tubules. These cords form in the central part of the yet-undifferentiated gonad, turning it into a testis. The now-induced Leydig cells of the testis then start secreting testosterone, while the Sertoli cells produce anti-Müllerian hormone.[8] SRY gene effects normally take place 6–8 weeks after fetus formation and inhibits the female anatomical structural growth in males.