Diethylstilbesterol was a drug given to women to ease their pregnancies. Unfortunately, it was later found to alter the reproductive tract of female fetuses. The mechanism of DES action is thought to involve the repression of the Hox genes that instruct the regional specificity of the M llerian duct. 17.8 Sex and the central nervous system. There is ample evidence that estrogen and testosterone can cause changes in the central nervous system.
Birds appear especially susceptible to hormonally induced changes in their behaviors.
17.9 Other sex determination proteins in Drosophila. Sex-lethal does not work alone, but in concert with several other proteins whose presence is essential for its function. Many of these proteins have other roles during development. 17.10 Conservation of sex-determining genes. While the pathways of sex determination appear to differ between humans and flies, the discovery of a human gene similar to doublesex suggests that there may be a common end point to the two pathways.