Today in “we guessed this, but peer-reviewed science makes for better citations,” researchers Brittany Croft et al. at Melbourne’s Murdoch Children’s Research Institute learned more about how a baby’s sex is determined; it’s not just about the X-Y chromosomes, but involves a “regulator” that controls the gene activity deciding whether we become male or female.
Croft explains, “The Y chromosome carries a critical gene, called SRY, which acts on another gene called SOX9 to start the development of testes in the embryo. High levels of the SOX9 gene are needed for normal testis development.”
Another member of the research team, Andrew Sinclair, expands, “…we identified XX patients who would normally have ovaries and be female but carried extra copies of these enhancers, (high levels of SOX9) and instead developed testes. In addition, we found XY patients who had lost these SOX9 enhancers, (low levels of SOX9) and developed ovaries instead of testes.”