Men may be homosexual because of their mother's genes. Scientists from the University of California at Los Angeles have found that the genetics of mothers who have multiple gay sons act differently than those of other women, reports HealthDay News.
Basically, it works like this: Every woman carries two X chromosomes, even though they only require one of them. So the human body routinely inactivates one of those X chromosomes at random. Normally, what happens is half of the X chromosomes go one way, while the second half go the other way. "It's like flipping a coin," study co-author Sven Bocklandt told HealthDay News. "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 this study of 97 mothers of gay sons and 103 mothers who did not have gay sons, 25 percent of the 44 women who had more than one gay son also processed their X chromosomes differently than normal. "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 explained to HealthDay News. "That's extremely unusual." Only 4 percent of the moms whose sons were not gay inactivated the chromosome in this way, as did 13 percent of the mothers who had just one gay son. Bocklandt said this phenomenon is typically seen only in families with major genetic irregularities. He said 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."
This isn't the final answer. As Dr. Ionel Sandovici, a genetics researcher at The Babraham Institute in Cambridge, England, pointed out to HealthDay News, most of the mothers of multiple gay sons didn't share the unusual X-chromosome trait. In addition, the study is small. The study findings were published in the journal Human Genetics.