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September 10, 2019

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There is no single ‘gay gene,’ study concedes

Like size or intelligence, sexual attraction isn’t defined by one gene alone, but is the result of the complex interplay between multiple regions of the genome and hard to pin environmental factors.

That’s the conclusion of an analysis conducted on half a million DNA profiles as part of a giant study by researchers in Europe and the United States published in the influential journal Science recently. Its authors hope to bury the notion, popularized in the 1990s, of the existence of an all powerful “gay gene” that determines sexuality in the way eye color is defined.

“We... found that it’s effectively impossible to predict an individual’s sexual behavior from their genome,” said Ben Neale, a member of MIT and Harvard’s Broad Institute, one of several organizations involved in the work.

Sexual orientation does have a genetic component, say the researchers, confirming previous smaller studies, notably on twins. But the effect is mediated by a myriad of genes.

“There is no single gay gene but the contribution of many small genetic effects scattered across the genome,” said Neale, who added that environmental factors, how a person is raised and where they live all play a part.

Take for example height: The genetic component is indisputable and linked to how tall your parents are or were. But other factors like nutrition during childhood play an important part.

The new statistical analysis revealed five points in our chromosomes, called loci, which appear closely linked to sexuality, though each individually has a “very small” influence. It also turns out that one of these markers is associated with hair loss, which suggests a link with the regulation of sexual hormones.

It’s believed these five markers could be just the beginning, with thousands more awaiting discovery in future.

“Genetics definitely plays a part, but nonetheless, it is possibly a minority part — and there is an unexplained environmental effect that one can never put a finger on exactly,” said Fah Sathirapongsasuti, a scientist from the company 23andMe, which contributed to the study.

The bulk of the data came however from the UK Biobank, mainly white people, among individuals responding to the question: Have you had sexual relations with a person of the same sex?

The authors were aware of the sensitivity surrounding the subject, with two of the co-authors mentioning that they themselves were gay.

Eager to avoid being misinterpreted, they also consulted with LGBTQ groups on the best way to communicate their findings, which they have summarized on a website

The LGBTQ advocacy group GLAAD praised the work, saying it “provides even more evidence that being gay or lesbian is a natural part of human life.”

In 1993, a genetic study on 40 families claimed to have identified the Xq28 gene as defining sexual orientation, but the new analysis refutes this.


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