September 8, 2019 at 3:05 pm EST | by Staff reports
No single gene, but genetics a one-third factor in gay sex
genetics, gay news, Washington Blade

NEW YORK — The findings of what is being touted as the largest-ever study of the role genetics plays in same-sex sexual behavior found that genetics plays about a third of the influence on whether someone has same-sex sex but there’s no single “gay gene,” the New York Times and many other outlets reported last week citing findings published in the journal Science.

The influence comes not from one gene but many, each with a tiny effect — and the rest of the explanation includes social or environmental factors — making it impossible to use genes to predict someone’s sexual orientation, the Times reports.

The study of nearly half a million people, funded by the National Institutes of Health and other agencies, found differences in the genetic details of same-sex behavior in men and women. The research also suggests the genetics of same-sex sexual behavior shares some correlation with genes involved in some mental health issues and personality traits — although the authors said that overlap could simply reflect the stress of enduring societal prejudice, the Times reports.

The study analyzed the genetic data of 408,000 men and women from a large British database, the U.K. Biobank, who answered extensive health and behavior questions between 2006-2010, when they were between the ages of 40-69. The researchers also used data from nearly 70,000 customers of the genetic testing service 23andMe, who were 51 years old on average, mostly American, and had answered survey questions about sexual orientation. All were of white European descent, one of several factors that the authors note limit their study’s generalizability. Trans people were not included, the Times reports.

The researchers mainly focused on answers to one question: whether someone ever had sex with a same-sex partner, even once.

A much higher proportion of the 23andMe sample — about 19 percent compared to about 3 percent of the Biobank sample — reported a same-sex sexual experience, a difference possibly related to cultural factors or because the specific 23andMe sexual orientation survey might attract more LGB participants, the Times reports.

Despite its limitations, the research was much larger and more varied than previous studies, which generally focused on gay men, often those who were twins or were otherwise related.

There might be thousands of genes influencing same-sex sexual behavior, each playing a small role, scientists believe. The new study found that all genetic effects likely account for about 32 percent of whether someone will have same-sex sex, the Times reports.

Using a big-data technique called genome-wide association, the researchers estimated that common genetic variants — single-letter differences in DNA sequences — account for between 8 percent and 25 percent of same-sex sexual behavior. The rest of the 32 percent might involve genetic effects they could not measure, they said.

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