In science, we don't often get to talk about male repression, but a new discovery gives us just such a chance. It turns out that ovaries can only remain ovaries by constantly suppressing their ability to become male. Silence a single gene, and adult ovaries turn into testes. That adult tissues can be transformed in this way would be surprising enough, but doing so by changing a single gene is truly astonishing.
As embryos, our gonads aren't specific to either gender. Their default course is a female one, but they can be diverted through the action of a gene called SRY that sits on the Y chromosome. SRY activates another gene called Sox9, which sets off a chain reaction of flicked genetic switches. The result is that premature gonads develop into testes. Without SRY or Sox9, you get ovaries instead.
