New research reported in Forbes magazine has added a twist to the debate on the origins of sexual orientation, suggesting that the genetics of mothers with multiple gay sons act differently than those of other women.

Scientists have reported that in nearly one-fourth of mothers with more than one gay son, X chromosomes were processed 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.

According to Forbes, 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,” according to the study’s co-author Sven Bocklandt, a postdoctoral researcher at the University of California at Los Angeles.

Scientists have been debating the issue of genetics and sexual orientation 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, Mr 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.”

“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.

In his 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.

“When we looked at women who have gay kids, in those with more than one gay son, we saw a quarter of them inactivate the same X in virtually every cell we checked,” Mr Bocklandt said. “That’s extremely unusual.”

And while researchers aren’t ready to say what exactly this means, the writer said he thinks he and his colleagues are moving closer to understanding the origins of sexual orientation.

“What’s really remarkable and very novel about this is that you see something in the bodies of women that is linked to a behavioural trait in their sons.”

“That’s new, that’s unheard of.”

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