Study links homosexuality in men to the way mothers process X chromosomes
New research suggests that mothers of multiple gay sons process X chromosomes differently than other women.
The study by a research team at the University of California at Los Angeles adds another bit of evidence that sexual orientation is at least in part due to genetics.
The research group found that about a quarter of the mothers who had more than one gay son processed X chromosomes in their bodies in the same way.
Ordinarily, women process the chromosomes randomly in one of two ways: half go one way, half go the other.
“This confirms that there is a strong genetic basis for sexual orientation, and that for some gay men, genes on the X chromosome are involved,” Sven Bocklandt, a co-author of the study, told HealthDay News. Bocklandt is a postdoctoral researcher at UCLA.
While women have two X chromosomes, they require only one and routinely inactivate the other, Bocklandt said.
Women typically inactivate one of their two X chromosomes randomly.
“It’s like flipping a coin,” Bocklandt told HealthDay News. “If you look at women in any given tissue, you’d expect about half the cells to inactivate one X, and half would inactivate the other.”
The researchers studied 97 mothers of gay sons and 103 mothers without gay sons to check for differences in the way they handled their X chromosomes. In women with more than one gay son, a quarter inactivated the same X chromosome in virtually every cell the researchers checked.
“That’s extremely unusual,” Bocklandt said.
In contrast, 4 percent of the mothers with no gay sons activated the same chromosome and 13 percent of those with just one gay son did.
Bocklandt said the study shows something happening in the bodies of women that is linked to a behavioral trait in their sons.
“That’s new,” he told HealthDay News. “That’s unheard of.”
Other researchers cautioned against reading too much into the study’s findings. They pointed out that most of the mothers of multiple gay sons 75 percent didn’t share the remarkable X-chromosome trait.
And the overall study size is small, which means additional research is needed to confirm the study’s results.
This article appeared in the Dallas Voice print edition, February 24, 2006.