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Latest study on homosexuality in men gives new evidence for role of genetics

genetic research

October 31, 1995
Web posted at: 10:45 a.m. EST

NEW YORK (CNN) -- Scientists have found new evidence that suggests male homosexuality has a genetic link. The research supports a similar study two years ago.

Researchers studied pairs of homosexual brothers, focusing on the X chromosome, which men inherit from their mothers. The new study suggests a particular portion of that chromosome helps influence whether a man is gay.

"Our result says that genes are involved in male sexual orientation, although they certainly do not determine a person's sexual orientation," said Dean Hamer, a researcher at the National Cancer Institute and author of the study. "There probably are other biological factors like hormones, for example, and other variables we simply don't know anything about yet."

Previous studies also have suggested a biological influence in sexual orientation, but scientists still can't explain what makes a person gay, heterosexual or bisexual. The study does not identify any specific gene. Hamer said there was no way to know how strongly the gene influences the development of male homosexuality.

Hamer worked with colleagues at the National Institute of Health, the University of Colorado at Boulder and the Whitehead Institute for Biomedical Research. They examined 32 pairs of exclusively or mostly gay brothers from unrelated families. Twenty-two pairs, or two-thirds, shared the same version of the genetic material, suggesting that it contains a gene predisposing the men to homosexuality.

Researchers looked for a similar effect in women but found no evidence to support the theory. The study appears in the November issue of the journal Nature Genetics.


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