How is sex determined in Drosophila and Humans?

The protein profile of each cell, in other words the amounts and types of proteins it expresses, determines its role in the development of the organism that it forms part of. Each cell is assigned a fate by the information encoded in the DNA of the organism, and these fates vary according to the location of the cell in relation to the original zygote cell. Protein signals from this central cell control the cell division …

…would be expected if the Sry gene initiated male development. The androgen receptor that receives the testosterone signal was analysed through the study of Tfm mice lacking this receptor. XY mice hemizygous for the X-linked Testicular femininisation mutation developed as females but were infertile and had testes. Thus the lack of receptors meant that even though these mice were producing testosterone, it was having no effect because it did not have anything to bind to.