Quantitative mRNA expression for SRY , SOX9 , AMH, FGF9, FOXL2, FST, RSPO1 and WNT4 during normal male (solid circles) and female (open circles) gonadal differentiation. Dotted line indicates day of birth, grey shading in a-d indicates the period of testis patterning and grey shading in e-h indicates the window of ovarian patterning. The critical period of testicular differentiation occurs between day 25 of gestation and day 2 postpartum, and that of ovarian differentiation between days 6-10 postpartum. P values from t-tests conducted to examine whether expression levels of the various genes were significantly different between males and females at each data point are shown in Additional file 1. Raw data for the mean ΔCt and standard deviations for each data point are shown in Additional file 5.