Sexual identity is wired into the genes, which discounts the concept that homosexuality and transgender sexuality are a choice, California researchers reported on Monday. "Our findings may help answer an important question--why do we feel male or female?" Eric Vilain, a genetics professor at the University of California, Los Angeles School of Medicine, said in a statement. "Sexual identity is rooted in every person's biology before birth and springs from a variation in our individual genome. Our findings may explain why we feel male or female, regardless of our actual anatomy. These discoveries lend credence to the idea that being transgender--feeling that one has been born into the body of the wrong sex--is a state of mind."
Vilain's team has identified 54 genes in mice that may explain why male and female brains look and function differently. Since the 1970s, scientists have believed that estrogen and testosterone were wholly responsible for sexually organizing the brain. Recent evidence, however, indicates that hormones cannot explain everything about the sexual differences between male and female brains. Published in the latest edition of the journal Molecular Brain Research, the UCLA study used two genetic testing methods to compare the production of genes in male and female brains in embryonic mice--long before the animals developed sex organs. They found 54 genes produced in different amounts in male and female mouse brains, prior to hormonal influence. Eighteen of the genes were produced at higher levels in the male brains; 36 were produced at higher levels in the female brains. The scientists plan to conduct further studies to determine the specific role for each of the 54 genes they identified.