A new UCLA study of chromosomes in 97 mothers of gay sons and 103 mothers without gay sons shows a difference in the occurrence rate of the way certain cells behave.

The cells in women each have two X-chromosomes, one of which is activated, and one of which is not. Usually, these activations are random so that on average half of her cells have one active chromosome and half have the other. In rare instances, all of the cells will have activated the same chromosome.

This study looked at the mothers of no gay sons, one gay son, and two or more gay sons and found that there was a significant difference in the incidences of single-chromosome activation.

“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.

This study certainly does not identify “the gay gene” or even, on its own, conclusively prove that the sexual orientation of all gay men is determined genetically.

Still, there are caveats. Dr. Ionel Sandovici, a genetics researcher at The Babraham Institute in Cambridge, England, pointed out that most of the mothers of multiple gay sons didn’t share the unusual X-chromosome trait. And the study itself is small, which means more research will need to be done to confirm its findings, Sandovici said.

If further research confirms the findings, however, this research adds to the growing evidence that sexual orientation – in some men, at least – has a basis in genetics.

Anti-gay activists have attacked the results of other studies that have indicated a genetic or biological basis to orientation. One of their methods has been to suggest that the causal relation between orientation and (for example) brain chemistry is the opposite of what has been presented, that homosexual activity caused a biological change rather than the other way around.

However, here that that argument is more difficult to make. The anti-gay activist is in the unenviable position of having to claim that sexual activity on the part of children changed the chromosome activation in their mothers.

We may, however, fully expect Dr. Throckmorton or another pet NARTH scientist to expound that this report means nothing. They will focus on the 3/4 of the women who did not share the trait and completely ignore the huge disparity (six times as high) in rate of occurrence between those who did have multiple gay sons and those who had none.

We at exgaywatch make no claim as to the basis of sexual orientation. It may be some combination of genetic, biological, or environmental factors. And these factors may be different between individuals. However those ex-gay ministries who make the sweeping claim that “no one is born gay” seem to have less and less basis for their claim.

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