from Clinical/Therapeutic Issues
The study was co-authored by postdoctoral researcher Sven Bocklandt at the University of California, LA. According to Bocklandt, his study "confirms that there is a strong genetic basis for sexual orientation, and that for some gay men, genes on the X chromosome are involved."
Bocklandt and his associates studied "X-chromosome inactivation" and surveyed 97 mothers with gay sons and 103 mothers without gay sons to see how they handled their X-chromosomes. "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," said Bocklandt. He also said: "What's really remarkable and very novel about this is that you see something in the bodies of women that is linked to a behavioral trait in their sons. That's new, that's unheard of."
Psychologist Dr. Warren Throckmorton has reviewed Bocklandt's study and commented on it on his blog on February 21:
This kind of stuff is interesting, of course, but the conclusions drawn by the researchers is speculative: "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 findings I read in the abstract do not "confirm" anything. Furthermore, the study as described could not provide any pathway from a putative genetic mechanism to behavior. All they have shown is there are group differences.
As I look at it, none of this is very enlightening unless the temperament and environment of the sons is also taken into consideration. There are potential intervening variables that are not even considered by these researchers (e.g., gender atypical temperaments). GAT may be related to these changes in the X chromosome but I doubt this was taken into account.
Issue: Volume 118, Number 6
Date: February 2006
Pages: 691 - 694
Extreme skewing of X chromosome inactivation in mothers of homosexual men
Sven Bocklandt, Steve Horvath, Eric Vilain and Dean H. Hamer
Abstract Human sexual preference is a sexually dimorphic trait with a substantial genetic component. Linkage of male sexual orientation to markers on the X chromosome has been reported in some families. Here, we measured X chromosome inactivation ratios in 97 mothers of homosexual men and 103 age-matched control women without gay sons. The number of women with extreme skewing of X-inactivation was significantly higher in mothers of gay men (13/97=13%) compared to controls (4/103=4%) and increased in mothers with two or more gay sons (10/44=23%). Our findings support a role for the X chromosome in regulating sexual orientation in a subgroup of gay men.