Saturday, February 25, 2006

The Gay Chromosome

It wouldn't be right if we didn't mention this new research supporting the hypothesis that sexual orientation has got a genetic component.
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.

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.

"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," Bocklandt said. "That's extremely unusual."

Forty-four of the women had more than one gay son.

In contrast, 4 percent of mothers with no gay sons activated the chromosome and 13 percent of those with just one gay son did. Moms' Genetics Might Help Produce Gay Sons

The "ex-gay" movement has a favorite motto that they chant everywhere they go: There is no gay gene. The motto is silly, to begin with. Take any other personality trait. Is there an extroversion gene? A sense-of-humor gene? A grace-and-charm gene? Even an intelligence gene? The truth is, the complete human being is the result of gazillions of genes interacting with one another and with the world; the phenotype results from the interaction of the genotype with the environment.

So to say there's no gene for something is just to admit that you don't understand how genes work.

I had to peek to see what Warren Throckmorton, the CRC's pet PhD, would say about this new research. He talks about it on his blog, and of course says the conclusions are "speculative." (He only read the abstract.) He complains:
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.

I'm sure he's not trying to say that this-or-that temperament would have changed the mother's X chromosome. He must mean the opposite, that the X chromosome causes "GAT," which in turn would predispose a person to be gay. So?

(Wow, I should note a rare phenomenon. The phrase "gender atypical temperament" in quotes gets exactly one hit on Google -- Throckmorton's Powerpoint from the CRC's meeting.) (I think it's a reference to Bem's theory of the development of homosexuality.)

Look, it's only a matter of time before sexual orientation is understood on the genetic level. Some factors will be identified that predispose a certain orientation. There will always be an element of opportunity, features of the environment that cause the tendency to be expressed, or not, and it will always be a probability game. But the nuts oughta be looking for something to replace "there's no gay gene," because time's about to run out on that one.

Those who cling to the idea that sexual orientation is a choice will find themselves backed into a corner, and soon. They want it to be a choice, but already most people, including most scientists, don't believe that.

Trust me, this paper didn't get through several rounds of review at a major journal on the basis of its political implications:
Human Genetics
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.


Anonymous Anonymous said...

Far from a milestone, this study doesn't add much and is easily refuted. I won't do so, however, unless Jim agrees not to delete the parts of the conversation he doesn't like.

February 27, 2006 10:23 AM  
Blogger JimK said...

Anon, I'm sure you can close your eyes tightly and this study will go away, no problem.

As far as your other comment. I have never deleted something because I disagreed with the opinion. I have deleted offensive, personal comments by you, and recently, one of the other administrators deleted some things you posted that were just articles cut-and-pasted out of the newspapers. If you have something to say, say it -- if you see an interesting article, post a link.

To accuse me of censoring the discussion here in order to favor my own point of view is an example of the kind of thing that makes people dislike you. You don't seem to be able to distinguish facts from beliefs that might be consistent with your point of view. Your very presence here, and the fact that you flood this blog with comments even while you're on the clock at CBM, that you insult everyone here on a daily basis, that you lie and make up "facts" and distort the evidence, is proof that we are very tolerant in this comments section. That is, we even tolerate you. And trust me, there has been more than once that someone has suggested we block your IP number!


February 27, 2006 10:50 AM  
Anonymous Anonymous said...

Let's see if anonymous is working on the clock or off while goofing off on this list. Will that CPA firm care about that? Will clients...?


February 27, 2006 2:45 PM  
Blogger Bill Ware said...

This is certainly an interesting study. Previously, I would have guessed that when the chromosomes from the egg and sperm originally get together during fertilization, various genetic and hormonal (chemical) influences would have resulted in one of the X chromosomes in females being turned off at that time. Once this initial selection occurred, it would then be carried forward through all subsequent cell divisions resulting in every cell in the body having the same X chromosome inactivated. So I am quite surprised that a survey of body cells finds that in most cases the selection of which X chromosome is inactivated is such a random event, apparently occurring during the latest cell division.

Searching for a specific "gay gene" appears to be folly. Many genetic an hormonal factors are surely involved, as they are in handedness. The end result of the interaction of these factors may simply be the selection, the turning on or off, of sets of genes related to the sex of the persons we are attracted to, gene sets that each of us already has. I describe these mechanisms in more detail here.

All in all, the study makes it hard for even the most diehard Freudian to explain how a child's upbringing could go back and influence the mother's X chromosome inactivating pattern. Additional comments about this study can be found here.

March 01, 2006 3:22 PM  
Anonymous Anonymous said...

Again, it "might" contribute to the sexual orientation.

Gay activists push further than what is said, and say, there is a genetic cause for homosexuality. Genetics may contribute to the devopment of a homosexual orientation, but it has never been shown to be the determining cause or source of same-sex attractions. That is the myth that has been widely spread for the last 15 years.

To be honest, research findings have changed very little in the 15 years, the media has highlighted this controvery. LeVay's original research and methologies were widely criticized, even by researchers who were gay themselves.

March 03, 2006 12:08 AM  
Blogger JimK said...

Anon, I don't think I've ever heard a gay activist say thete was a "genetic cause for homosexuality." There probably is, might not be; at any rate, they do say it's not a choice -- which is not even remotely the sme thing. That is, it is not true that everything in life that is "not a choice" is genetic.


March 03, 2006 6:56 AM  
Blogger Bill Ware said...


Thanks. Here's something about handedness which points out how we know a trait is genetic even though it doesn't follow the pure Mendelian inheritance pattern.

March 04, 2006 6:22 PM  
Anonymous Anonymous said...

Eunuchs are also another proof

June 01, 2014 12:30 AM  

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