Ovaries form and produce the female hormone estrogen. But this work shows that the activity of a single gene, FOXL2, is all that prevents adult ovary cells turning into cells found in testes. The identification of an individual as either biologically male or female can have legal ramifications for marriage licenses, spousal support and eligibility for parenthood. Without it, girl genes are activated. Ford and his team, in the wake of Jost's experiments, discovered  that the Y chromosome was needed for a fetus to develop as male when they examined patients with Turner's syndrome , who grew up as phenotypic females, and found them to be X0 hemizygous for X and no Y. It turns out that the sex determination pathway is probably more complicated and SRY may in fact inhibit some anti-male genes. These genes reduce male gene activation and increase it, respectively. The internal and external sexual organs of boys and girls developed from the same basic body plan, but you know, at birth, you can clearly distinguish the 2 sexes just by looking. The ZZ become males, but the WW are not viable and are not brought to term. Affected individuals are usually taller than average and have slender builds. The presence of Y chromosome genes is required for normal male development. Clitoral surgery for intersex conditions was promoted by Hugh Hampton Young in the United States in the late s. However, homologues to the avian DMRT1 gene on platypus sex chromosomes X3 and X5 suggest that it is possible the sex-determining gene for the platypus is the same one that is involved in bird sex-determination.