Genes, Not Genitalia, Are Key to Gender

Experts say more research, understanding needed for those of ambiguous sex

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FRIDAY, Feb. 18, 2005 (HealthDay News) -- Genetics, not just anatomy or hormones, strongly influence gender, according to research that raises questions about sex-assignment surgeries for babies born with both male and female traits.

"The biology of gender is far more complicated than XX or XY chromosomes, and may rely more on the brain's very early development than we ever imagined," genetics and sexual medicine expert Dr. Eric Vilain, said in a prepared statement.

Vilain was a member of a special panel convened Feb. 18 at the American Association for the Advancement of Science annual meeting in Washington, D.C.

Experts estimate that immediate gender assessment is impossible in about one in 4,000 to one in 5,000 newborns, due to "intersex" conditions that affect their genitalia, reproductive systems or sex chromosomes.

"Surgical sex assignment of newborns with no capacity to consent should never be performed for cosmetic reasons, in my opinion; we simply don't know enough yet about gender to be making surgical or legal assumptions," contended Vilain, an associate professor of human genetics, chief of medical genetics, and director of research in urology and sexual medicine at the David Geffen School of Medicine at University of California, Los Angeles.

Dr. William G. Reiner, a psychiatrist and an associate professor in the department of urology at Oklahoma University Health Science Center, agreed. "The most important sex organ is the brain," he said in a prepared statement. "We have to let these children tell us their gender at the appropriate time."

However, most laws in the United States assume that every person is clearly a male or female, and many children with ambiguous genitalia continue to undergo surgical sex assignment, according to Cleveland State University legal expert Susan Becker.

"The U.S. Constitution promises equality, rights and benefits for all citizens. But, as the Constitution is structured and interpreted, individuals who do not meet the binary definition for male versus female don't have the same benefits and aren't completely protected from discrimination," she said in a prepared statement.

A wide variety of genes may hold the keys to gender, Vilain said. In ongoing research, his team at UCLA has identified 54 different genes that expressed differently in the brains of male and female embryonic mice soon after conception.

"Differences of gene expression between male and female brains, very early on, suggest that our brain may be hard-wired at a very early stage to become male or female," he said.

More information

The U.S. National Library of Medicine has more about ambiguous genitalia.

SOURCE: American Association for the Advancement of Science, news release, Feb. 18, 2005


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