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Research: Study Casts Doubt on 'Gay' Gene

A Christian Response to AIDS: Research


Canadian research fails to replicate earlier U.S. work


April 22 — Researchers in Canada cast doubt on the idea of a “gay gene” on Thursday, saying they had been unable to find any genetic link between brothers who are homosexual. In 1993, Dr. Dean Hamer and colleagues at the U.S. National Cancer Institute provoked a worldwide furor when they reported they had found evidence of a “gay gene” in men.

The researchers said it was possible there was another “gay gene,” as the team only looked at one gene for its study.

IN THE EARLIER report, researchers concluded that 33 of 40 pairs of gay brothers shared a set of genetic markers in an area of the X chromosome known as Xq28. Based on the discovery of these markers, called DNA sequences, the researchers postulated that a gene in this location could explain some instances of male homosexuality.

But in a study published in this week’s Science, George Rice and colleagues at the University of Western Ontario in London, Canada, said they studied more pairs of gay brothers and found no evidence that they shared some sort of mutation in that area. They examined blood samples taken from 52 pairs of gay brothers and found that the rate of shared genetic markers at Xq28 was no higher than would have been expected by chance.


Even though the researchers were not able to confirm Hamer’s findings, Rice and his colleagues did not rule out other genetic links to homosexuality. He said his team is still looking for such evidence in other locations.

The researchers said it was possible there was another “gay gene,” as the team only looked at one gene for its study.

Men, in addition to their 22 pairs of matched chromosomes, have one X and one Y chromosome. Women have two Xs.

Men inherit their X chromosomes from their mothers, and because they have just one copy, are vulnerable to genetic defects carried on the X chromosome such as color blindness and Fragile X syndrome, which causes a form of mental retardation.

Hamer’s team had noted a tendency for homosexuality to run in the female line — men whose mothers had gay brothers also tended to be homosexual, the team reported. So it looked for an area on the X chromosome that might be involved. The team homed in on an area known as Xq28.

Studies dating back to the 1980s show some evidence that homosexuality might run in families. One study on identical twins, who share more of their genes than regular siblings, found one twin was more likely to be gay if his twin was, and another study found homosexual men were more likely to have homosexual brothers even if they were not twins.


Another scientist who has conducted research on the subject said it is too early to make a final decision. “I don’t think that Rice’s paper rules out that there could be an important gene in this area,” said Dr. Alan Sanders, an assistant professor of psychiatry at the University of Chicago.

When scientists try to reproduce the findings of another research team, the results can be complicated, according to Sanders. Sometimes the second study arrives at the same conclusion, which bolsters the original idea. Other times the research contradicts the earlier work, Sanders said.

“We’ve got to wait and see,” he said, adding that studies that involve larger numbers of participants should help to produce more definitive findings.

The Medical Tribune News Service and Reuters contributed to this report. [This report appeared on MSNBC online, April 22, 1999.]

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