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TUESDAY, Feb. 21 (HealthDay News) -- New research adds a twist to the debate on the origins of sexual orientation, suggesting that the genetics of mothers of multiple gay sons act differently than those of other women.
Scientists found that almost one fourth of the mothers who had more than one gay son processed X chromosomes in their bodies in the same way. Normally, women randomly process the chromosomes in one of two ways -- half go one way, half go the other.
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The research "confirms that there is a strong genetic basis for sexual orientation, and that for some gay men, genes on the X chromosome are involved," said study co-author Sven Bocklandt, a postdoctoral researcher at the University of California at Los Angeles.
The link between genetics and sexual orientation has been a hot topic for more than a decade as a few scientists have tried to find genes that might make people gay or straight. In the new study, Bocklandt and colleagues examined a phenomenon called "X-chromosome inactivation."
While females have two X chromosomes, they actually require only one and routinely inactivate the other, Bocklandt said. "That way, both men and women have basically one functional X chromosome," he added. Men have both an X and Y chromosome, but the Y chromosome plays a much smaller role, he said.
Women typically inactivate one of their two X chromosomes at random. "It's like flipping a coin," Bocklandt said. "If you look at a woman in any given (bodily) tissue, you'd expect about half of the cells to inactivate one X, and half would inactivate the other."
In the new study, researchers looked at 97 mothers of gay sons and 103 mothers without gay sons to see if there was any difference in how they handled their X chromosomes. The findings appear in the February issue of the journal Human Genetics.
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