Published: Mon, September 02, 2019
Sci-tech | By Patricia Wade

Expansive study finds no single "gay gene" behind same-sex attraction

Expansive study finds no single

Reference: "Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior" by Andrea Ganna, Karin J.H. Verwe, Michel G. Nivard, Robert Maier, Robbee Wedow, Alexander S. Busch, Abdel Abdellaoui, Shengru Guo, J. Fah Sathirapongsasuti, 23andMe Research Team, Paul Lichtenstein, Sebastian Lundström, Niklas Långström, Adam Auton, Kathleen Mullan Harris, Gary W. Beecham, Eden R. Martin, Alan R. Sanders, John R.B. Perry, Benjamin M. Neale, and Brendan P. Zietsch, 30 August 2019, Science.

There might be thousands of genes influencing same-sex sexual behavior, each playing a small role, scientists believe.

"This study is the largest and most thorough investigation into the genetics of same-sex sexual behavior to date", said Director of Genetics in the Stanley Center for Psychiatric Research at the Broad Institute of MIT and Harvard University, study author Ben Neale.

The study's authors analyzed the patients' responses and performed genome-wide association studies on data from more than 477 522 people. (B) Among participants reporting at least one same-sex partner, those with a greater proportion of same-sex partners have a larger reproductive disadvantage.

Sexual behavior is highly complex and can not be simplistically defined by any single factor, according to the results of the largest study on the genetics of sexual behavior. For example, one marker identified was linked with balding, suggesting that sex hormone regulation may somehow be involved in same-sex sexual behavior.

These variants, together with 1000's of others within the human genome which have even smaller results, collectively accounted for eight% to 25% of variation in same-sex sexual conduct, the evaluation confirmed.

However, the researchers have emphasised that the study does not suggest that same-sex sexual behaviour either causes or is caused by these conditions.

David Curtis, honorary professor at the UCL Genetics Institute, University College London, said: "This study clearly shows that there is no such thing as a "gay gene".

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QaziRahman, a leading authority on sexual orientation research from King's CollegeLondon, welcomed the study but said that the databases involved only capturedinformation from a small percentage of people who were invited to participate.That, he said, means that the genetic variants found in the latest researchmight reflect another trait particular to those who chose to respond.

"Genetics is less than half of this story for sexual behavior but it's still a very important contributing factor", Neale added.

Because of the complexity of the genetic influences, we can not meaningfully predict a person's sexual preference from their DNA - nor was this our aim. For instance, research has shown patterns in families with multiple men in the same family identifying as gay.

Interestingly, just 40 percent of genetic influences were shared by both sexes while the other 60 percent were unique to each sex.

The researchers are an worldwide group co-led by Benjamine Neale of the Broad Institute of MIT and Harvard and Brendan Zietsch of the University of Queensland in Australia.

The findings might strengthen legal protections for people in the LGBTQ community, says Melinda Mills, a social sciences and genetics researcher at the University of Oxford, who did not work on the study. The study does not allow any conclusive statements about the degree to which "nature" and "nurture" influence sexual orientation.

There are limitations to the new research.

Associate Professor Greg Neely at the University of Sydney told Science Media Centre that "a major weakness of this study is that it is primarily based on data from 40- to 70-year-old people across the United Kingdom". Researchers scanned their genomes to uncover whether there are genes associated with same-sex attraction. And same-sex attraction might be underrepresented "based on societal pressure from a previous era", he said. "It captures real-life experiences rather than trying to put people into bins that are always arbitrary".

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