Is There a 'Gay Gene'?
New Genetic Regions Associated With Male Sexual Orientation Found
Search for Gay Genes
In the study, researchers analyzed the genetic makeup of 456 men from 146 families with two or more gay brothers.
The genetic scans showed a clustering of the same genetic pattern among the gay men on three chromosomes -- chromosomes 7, 8, and 10. These common genetic patterns were shared by 60% of the gay men in the study. This is slightly more than the 50% expected by chance alone.
The regions on chromosome 7 and 8 were associated with male sexual orientation regardless of whether the man got them from his mother or father. The regions on chromosome 10 were only associated with male sexual orientation if they were inherited from the mother.
Mustanski compares the study's approach to a search for doctors in a town of 40,000 people, a number that roughly corresponds to the number of human genes.
Rather than guessing that doctors live in a particular type of house and going to only the houses that meet that criteria, researchers in this scenario would knock on every door to ask the residents if a doctor lives on their street. Using a similar approach, researchers were able to locate a few potential genetic neighborhoods that likely contribute to male sexual orientation.
Researchers say the next step is to verify these results in a different group of men to see if the same genetic regions are associated with sexual orientation. If the findings hold up, then Mustanski says they could start to look for the individual genes within these regions linked to sexual orientation.
New Targets for Gay Gene Research
Elliot S. Gershon, MD, professor of psychiatry and human genetics at the University of Chicago, says the study represents an important step forward in understanding how genes affect human sexual orientation.
"It is worth testing genes within a region of linkage to see if one of them has a variant that is more frequent in men who are gay than in men who are not," says Gershon, who is also currently involved in another study of gay brothers and genetic influences on sexual orientation.
"This report adds to the legitimacy of research on normal variations in human behavior," Gershon tells WebMD. "There is an argument that has been made in public press that it doesn't make sense to study conditions or traits that are behavioral. But this suggests that there is a genetic contribution to this particular trait of same sex orientation."