Normally in each cell of a female body one of the two X chromosomes has been deactivated by the placement of methyl groups (a carbon and 3 hydrogens) along the backbone of the DNA double helix. That deactivation is random. Suppose there are two X chromosomes in a woman called A and B where the A chromosome came from her mother and the B chromosome came from her father. In approximately half of the cells the A's will be deactivated and in the other half of the cells the B's will be deactivated. Well, in women who have gay sons the deactivation of the X chromosomes is skewed with one of the X's more often deactivated than the other.
But when Sven Bocklandt of the University of California, Los Angeles, compared blood and saliva samples from 97 mothers of gay men with samples from 103 mothers without gay children he found this process was extremely skewed in the mothers with gay sons, with one X chromosome being far more likely to be inactivated than the other. Only 4% of the mothers without gay sons showed this skewing, compared with 14% of mothers with at least one gay son. Among mothers with two or more gay sons, the figure was 23%.
This result suggests that eventually any woman will be able to have a genetic test done what will predict the odds that one of her sons will be born homosexual.
One can easily imagine all sorts of responses to this. It is safe to say that most women and most men do not want to have homosexual children. The degree of that preference varies and some people do not have a strong preference against their own children being homosexual. There is no doubt even a minority of people who would prefer their children to be homosexual.
So will women who are at greater risk of having homosexual sons become more reticent to have children? Or will they use reproductive technologies such as MicroSort to tip their odds toward having a daughter instead?
One question unanswered by this study is whether the skewing of X chromosome shut-down also increases the odds of lesbianism. The mechanism for producing lesbian female children may be (and I'm guessing is) entirely unrelated to the mechanism for producing homosexual sons. But a follow-up study could easily answer this question by repeating the same analysis with the mothers of lesbian daughters.
Of course, understanding of a genetic mechanism for the development of homosexuality will eventually lead to the development of treatments to alternatively prevent or cause a homosexual outcome. One question I do not have a guess about is whether control over sexual orientation of offspring will produce more or fewer homosexuals. You might argue that since most people either prefer heterosexual children or have no preference (or are at least so politically correct that they won't publically admit to a preference) it is hard to see how control over sexual orientation could increase the number of homosexuals. But there is one big point to consider: It takes only a small fraction of the population to choose having a homosexual child to increase the number that are born. Suppose that only 3% of male births are homosexual. It would take only 1 in 20 women (or gay men who hire a surrogate woman to carry a baby) deciding they'd rather have homosexual son to increase the number born.
My guess is that there is a greater chance that control of reproduction could increase the number of lesbians. After all, it is women who carry the babies, not men. Will most lesbian women want to have heterosexual or homosexual daughters? Anyone have a reason to think they know the answer?
This question of preferences for offspring sexual orientation is part of what I consider to be a huge coming issue: when people can control more characteristics of their offspring what choices will they make? Some choices are not hard to guess. People will want their kids to be smarter and better looking. But what will be the chosen frequency of, say, blondness or introversion versus extroversion? Or height? Tall overall is my guess. But how much taller? Will the distribution of heights become narrower since people won't want to burden their kids with excessive height? (that is my guess). Will personality choices for offspring become problematic for society as a whole? See my posts Altruistic Punishment And Genetic Engineering Of The Mind and Brain Rewards For Carrying Out Altruistic Punishment for more on that question.
By Randall Parker at 2004 November 09 04:26 PM Brain Genetics | TrackBackAny idea when this will be published?
>Will most lesbian women want to have heterosexual or homosexual daughters?
From the ones I've known well enough to talk about it, they have all expressed preference for gay sperm donors. From the literature I've read, the majority seem to prefer that their children also be gay, but acknowledge that their kids appear to have a higher percentage of heterosexuals than heterosexual couples do.
Yeah, I agree with Podcaster on that one. You can't forget about the miniature hippos on those cold days. They are likely to freeze up causing a huge atomical explosion with the power of a stick of firewood.
Okay, couple questions I can't find answers for on other sites either:
Of the X chromosomes in the woman who's the mother of the gay children, it says the deactivation is skewed towards one of her parents' X's being deactivated more often. Which one, the one she got from her mother or the one from her father?
Were these women's parents also involved in the study so they can determine which X came from where? If not, how could you tell which X came from which parent?