How to become a boy

Now this is weird.

(F)ully-developed adult females can undergo a partial sex change following a genetic modification to a single gene. The findings suggest that being male or female is not a permanently fixed state but something that has to be continually maintained in the adult body by the constant interaction of genes to keep the status quo – and the gender war – from slipping in favour of the opposite sex.

The results could explain some of the great mysteries of human gender, for instance why some women after the menopause develop male characteristics, such as facial hair and deeper voices, or why other people are so unhappy with the gender they were born with that they seek hormone therapy and radical sex-change operations.

Scientists said that the study also contradicted another biological dogma – that the "default" gender is female, with all embryos starting out as female unless they possess a male sex-determining gene. Although this remains true in terms of how gender is determined in the womb, the latest findings show that it is still possible to convert an adult female's ovaries into testosterone-producing testes.

Think of the implications of this, once it becomes easy to do, and all the questions it raises now.

• Imagine a woman athlete (or CEO, or actor) who converts her ovaries to testes to get an advantage from the increased testosterone.
• If one gene can change ovaries to testes, is there a set of genes that can grow a penis on a girl if you start soon enough after birth? Could a child with ambiguous sexuality, if he starts to think he's a boy, be able to develop one with gene therapy?
• Imagine women using it for birth control.
• Can it go the other way? I can't imagine balls developing eggs, but can they be changed to secrete female hormones? Could men grow functional (or even ornamental) breasts?
• Can you select which male characteristics to take on, such as maybe keeping aggression but dropping the beard and desire to watch NASCAR.
• This would explain how fish change sex. In the real world, when Nemo's mother died, his father would have turned female, and the biggest offspring would become the dominant male. Sheephead also change sex.

God, I love conjectural science.

UPDATE: Comment from somebody knowledgeable.