In the first week after conception the configurations that will become the reproductive organs or gonads are the same in males and females. Differentiation starts about 6 weeks after conception and genetic signals define whether the mass of undifferentiated sexual tissue matures into male or female gonads. At this time SRY gene product in a male fetus triggers the change of embryonic gonads into testes. In the absence of SRY and possibly under the influence of DSS or other femaleness gene, the undifferentiated gonadal tissue matures into ovaries. Once the testes or ovaries mature, those hormones become the serious factor in further sex differentiation and genetic influence ceases.