Scientists looking into the genetic basis for sexual orientation say they have discovered genes that can be linked to homosexuality.
Researchers who looked at the complete genome – a person’s entire DNA code – for more than 1,000 gay men and compared it to genetic data from a similar number of heterosexuals, found the DNA was different for gay and straight men in at least two genes.
But British experts said more work was needed before it was possible to say conclusively that “gay genes” could be identified.
One gene the American scientists found, SLITRK6, plays an important role in brain development, and is particularly active in a region of the brain that includes the hypothalamus, which is crucial for producing the hormones that control sex drive. Previous studies have shown parts of it can be up to 34 percent bigger in gay men.
The scientists, from North Shore University Health System’s Research Institute, in Illinois, also discovered differences in the TSHR gene, which is linked to the thyroid, another area associated with sexual orientation.
Dr Alan Sanders, lead author of the study, said: “Because sexuality is an essential part of human life – for individuals and society – it is important to understand the development and expression of human sexual orientation.”
Participants in the study were rated for sexual orientation based on their self-reported sexual identity and sexual feelings and provided their DNA for analysis.
However, British scientists said the genetic differences could point to other traits among the homosexual respondents. For example, the variations may simply predispose people to be more open or candid about their lives.
Prof Robin Lovell-Badge, of the Francis Crick Institute, said: “The topic of this paper is important if we are to learn more about the influence of genes on aspects of our behaviour, but this is notoriously difficult to study.
“Even if a gene variant does show some correlation with sexual orientation, this does not mean that the gene is in any way responsible for being gay – it just means it has some association with a trait that is more likely to be found in the relatively few people involved in the study. This could be better social awareness or being brave enough to acknowledge they are in a minority.”
Gil McVean, Professor of Statistical Genetics at the University of Oxford, also added: “Sexuality is likely influenced by many different factors, including environment, experience and, likely, some aspects of innate biological variation. I can see no major implications of this work or how it could be useful in the future.
“The genetic effects are far too weak to be of any predictive or diagnostic value. All biology – including the origins of sexuality – is interesting at some level, but I see no direct applications of such research.”