11.   They achieved this feat by prodding the activity of a single gene called CREB, which functions as a kind of master switch that unlocks dozens of other genes.

12.   A mutation somehow created a gene called SRY -- for sex-determining region Y -- and it became the master switch for creating a male, they said.

13.   The process of making a mammal embryo male is activated by a genetic master switch called SRY, which was discovered several years ago.