Figure 11

Timing of meiosis and retinoic acid metabolism during gonadal development in chicken embryos. Male shown in blue, female shown in pink. Gonadal sex differentiation begins at day 6.0. In the male gonads, RALDH2 and CYP26B1 are both highly expressed and meiosis does not occur during embryogenesis. In the left female gonad, RALDH2 is highly expressed, becoming concentrated in the cortex as it proliferates. CYP26B1 expression is down-regulated after E10.5, and is excluded form the cortex. At E12.5, STRA8 is up-regulated in the left gonad, and, at, E15, pre-meiotic DNA synthesis begins [31]. Meiosis is detectable histologically from E15.5.