Los Angeles, USA
— Sexual identity is wired into the genes, which
discounts the concept that homosexuality and transgender
sexuality are a choice, California researchers reported
on Monday, Oct. 20, 2003.
"Our findings may help
answer an important question -- why do we feel male or
female?" Dr. Eric Vilain, a genetics professor at the
University of California <http://www.berkeley.edu/>,
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." His 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
<http://www.sciencedirect.com/science/journal/00068993>,
the UCLA discovery may also offer physicians an improved
tool for gender assignment of babies born with ambiguous
genitalia. Mild cases of malformed genitalia occur in 1
percent of all births -- about 3 million cases. More
severe cases -- where doctors can't inform parents
whether they had a boy or girl -- occur in one in 3,000
births.
"If physicians could
predict the gender of newborns with ambiguous genitalia
at birth, we would make less mistakes in gender
assignment," Vilain said.
Using two genetic testing
methods, the researchers compared 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.
"We discovered that the
male and female brains differed in many measurable ways,
including anatomy and function." Vilain said. For
example, the two hemispheres of the brain appeared more
symmetrical in females than in males. According to
Vilain, the symmetry may improve communication between
both sides of the brain, leading to enhanced verbal
expressiveness in females.
"This anatomical
difference may explain why women can sometimes articulate
their feelings more easily than men," he said. The
scientists plan to conduct further studies to determine
the specific role for each of the 54 genes they
identified.
"Our findings may explain
why we feel male or female, regardless of our actual
anatomy," said Vilain. "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.
