Scientists Discover Way to Predict Male Homosexuality Using Genetics

There is no "gay gene," but methylation patterns uncovered using machine learning may provide insight into the genetics of sexuality.

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Scientists presenting at the American Society of Human Genetics 2015 annual meeting in Baltimore have announced the discovery of a gene-based algorithm capable of predicting homosexuality in men with up to 70 percent accuracy.

“To our knowledge, this is the first example of a predictive model for sexual orientation based on molecular markers,” said lead author Dr. Tuck C. Ngun of UCLA’s David Geffen School of Medicine in a press release.

While the study doesn’t identify a single “gay gene” — arguably the most controversial concept in studies on homosexuality — it does identify modification patterns in certain DNA regions that were associated with sexual orientation. Specifically, the researchers looked at differences in the way methyl groups, tiny clusters of hydrogen and carbon molecules, were attached to genes. Methylation, as the process is known, is one way the body turns certain genes on and off in response to environmental factors. To do this, it was integral to the study to compare individuals with the exact same DNA. The researchers looked at sets of identical twins. They focused on 37 pairs in which one twin was homosexual and the other was heterosexual, as well as 10 pairs in which both twins were homosexual.

The algorithm uncovered nine regions of the genome where methylation patterns predictably differed between homosexual and heterosexual twins. By analyzing these differences, the researchers could predict the sexual orientation of the twins. Identifying methylation patterns and regions of DNA that are relevant to sexual orientation is one thing, but explaining why they’re important will take a lot more research. Dr. Ngun acknowledges that there’s a lot we don’t understand about the molecular basis of sexual attraction, and he’s now testing his algorithm on a broader group of men.

“Sexual attraction is such a fundamental part of life, but it’s not something we know a lot about at the genetic and molecular level. I hope that this research helps us understand ourselves better and why we are the way we are,” Dr. Ngun said in a statement.

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