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Message: <blockquote data-quote="ex-muslim Ahmed" data-source="post: 18101810" data-attributes="member: 179431">Study of gay brothers may confirm X chromosome link to homosexuality<a href="http://news.sciencemag.org/biology/2014/11/study-gay-brothers-may-confirm-x-chromosome-link-homosexuality" target="_blank">Science article</a>Kelly is a staff writer at Science.By Kelly Servick 17 November 2014 11:00 amDean Hamer finally feels vindicated. More than 20 years ago, in a study that triggered both scientific and cultural controversy, the molecular biologist offered the first direct evidence of a “gay gene,” by identifying a stretch on the X chromosome likely associated with homosexuality. But several subsequent studies called his finding into question. Now the largest independent replication effort so far, looking at 409 pairs of gay brothers, fingers the same region on the X. “When you first find something out of the entire genome, you’re always wondering if it was just by chance,” says Hamer, who asserts that new research “clarifies the matter absolutely.”But not everyone finds the results convincing. And the kind of DNA analysis used, known as a genetic linkage study, has largely been superseded by other techniques. Due to the limitations of this approach, the new work also fails to provide what behavioral geneticists really crave: specific genes that might underlie homosexuality.Few scientists have ventured into this line of research. When the genetics of being gay comes up at scientific meetings, “sometimes even behavioral geneticists kind of wrinkle up their noses,” says Kenneth Kendler, a psychiatric geneticist at Virginia Commonwealth University in Richmond. That’s partially because the science itself is so complex. Studies comparing identical and fraternal twins suggest there is some heritable component to homosexuality, but no one believes that a single gene or genes can make a person gay. Any genetic predispositions probably interact with environmental factors that influence development of a sexual orientation.Several genomic studies have suggested regions that might influence sexual orientation, but they have relied on small numbers of participants and have been challenged repeatedly. In 1993, Hamer, then at the U.S. National Institutes of Health (NIH) in Bethesda, Maryland, published the first of these studies, suggesting that a specific stretch of the X chromosome called Xq28 holds a gene or genes that predispose a man to being gay.The finding made some evolutionary sense. An X-linked gene for homosexuality has long been proposed as a way to explain how the trait persists in the population even though gay men tend to have fewer offspring: The gene could increase fertility in females, who would have two “chances” to inherit it.</blockquote>

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