DNA differences are linked to having same-sex sexual partners

EWS

GENETICS

The specific genes involved in mate choice aren’t yet known

BY TINA HESMAN SAEY 10:32AM, OCTOBER 20, 2018

“GAY GENES” New research has uncovered DNA differences linked to same-sex sexuality in both men and women. Those genetic tweaks don’t predict who is likely to be gay.一项新的研究发现，男性和女性的DNA差异与同性性行为有关。这些基因调整并不能预测谁可能是同性恋。

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Magazine issue: Vol. 194, No. 9, November 10, 2018, p. 10

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SAN DIEGO — For some people, choosing a same-sex partner may be in their DNA.对一些人来说，选择同性伴侣可能是他们的基因。

In a large study of more than 490,000 men and women in the United States, United Kingdom and Sweden, researchers discovered four genetic variants that occur more often in people who indicated on questionnaires that they had had same-sex sexual partners. Andrea Ganna, a at the Broad Institutegeneticist of MIT and Harvard 麻省理工学院和哈佛大学布罗德研究所的遗传学家reported the results October 19 at the annual meeting of the American Society of Human Genetics. Two of the variants were specific to men’s sexual partner choice. The other two influence sex partner choice for both men and women.

Collectively, the DNA differences explained only 8 to 12 percent of the heritability of having same-sex partners.总的来说，DNA差异只解释了拥有同性伴侣的遗传可能性的8%到12%。 “There is no gay gene,” Ganna said, “but rather non-heterosexuality is influenced by many tiny-effect genetic factors.”“没有同性恋基因，”Ganna说，“但是非异性恋受许多微小影响的遗传因素影响。

The new study is an advance over previous attempts to find “gay genes,” says J. Michael Bailey, a psychologist at Northwestern University in Evanston, Ill., who was not involved in the new work. 位于伊利诺斯州埃文斯顿的西北大学(Northwestern University)的心理学家j·迈克尔·贝利(J. Michael Bailey)说，这项新研究比以往试图找到“同性恋基因”的努力有所进步。他没有参与这项新工作。The study’s size is its main advantage, Bailey says. “It’s huge. Huge.”

Researchers examined DNA data from more than 400,000 participants in the U.K. Biobank and more than 69,000 people who had their DNA tested by the consumer testing company 23andMe. People who have given their DNA data to those research projects also answered a battery of questions, including ones about whether they had ever had a partner of the same sex and how many sexual partners they have had. 向这些研究项目提供DNA数据的人还回答了一系列问题，包括他们是否有过同性伴侣，以及他们有过多少性伴侣The findings were replicated with data from three other studies, including one from Sweden. Findings from such large studies are more likely to be replicated than the small studies in the past, Bailey says. Researchers have “really gotten these studies down now and if they find things, it’s pretty sure that they’re true.”

Previous sexual orientation genetic studies, including some Bailey was involved in, may also have suffered from bias because they relied on volunteers.之前的性取向基因研究，包括贝利参与的一些研究，也可能因为依赖志愿者而遭受偏见 People who offer to participate in a study, without being randomly selected, may not reflect the general population, he says. This study includes both men and women and doesn’t rely on twins, as many previous studies have, he says. “It’s a huge advance … but it doesn’t tell us everything we need to know.”

For instance, the study doesn’t address people’s attraction to members of the same sex. Some people who have had sex with a same-sex partner don’t consider themselves gay and aren’t exclusively attracted to people of the same sex, Bailey says.贝利说，一些与同性伴侣发生过性行为的人并不认为自己是同性恋，也不完全被同性所吸引。 He calls the study’s definition of non-heterosexual behavior as having ever had a same-sex partner “a flawed, but not ridiculous indicator of sexual orientation.”他称该研究对非异性恋行为的定义为曾经有过同性伴侣，这是“一个有缺陷的，但并不荒谬的性取向指标”。

Men in the new study who said they have had same-sex partners, tended to be more exclusively homosexual than women were, Ganna and colleagues found.Ganna和她的同事们发现，在这项新的研究中，那些声称自己有过同性伴侣的男性往往比女性更倾向于成为同性恋。 But people of both sexes ran the gamut of sexual orientations. 但是，男性和女性的性取向却各不相同。In the U.K. Biobank dataset, for example, younger people reported having same-sex partners more often than older people did, probably because homosexual activity was illegal in the United Kingdom until 1967.

‌This is not the only complex human for which we see a genetic influence without a great understanding of how that influence works.这并不是唯一一种复杂的人类现象，我们看到了遗传的影响，而对这种影响是如何起作用却没有很好的理解。

— Lisa Diamond

This is the first DNA difference ever linked to female sexual orientation, says Lisa Diamond, a psychologist at the University of Utah in Salt Lake City who studies the nature and development of same-sex sexuality. The results are consistent with previous studies suggesting genetics may play a bigger role in influencing male sexuality than female sexuality. It’s not unusual for one sex of a species to be more fluid in their sexuality, choosing partners of both sexes, Diamond says.戴蒙德说，一个物种的一种性别在性方面更加灵活，选择两性伴侣，这是很正常的 For humans, male sexuality may be more tightly linked to genes.

But that doesn’t mean that genes control sexual behavior or orientation. “Same-sex sexuality appears to be genetically influenced, but not genetically determined,” Diamond says. “This is not the only complex human phenomenon for which we see a genetic influence without a great understanding of how that influence works.” Other complex human behaviors, such as smoking, alcohol use, personality and even job satisfaction all have some genetic component.遗传因素

Previous research had suggested that genes influencing sexual orientation were located on the X chromosome (SN: 11/4/95, p. 295; SN: 7/7/93, p. 37). But Ganna and colleagues found no evidence that the X chromosome is involved in partner choice, he said.

Instead, the researchers found genetic variants known as single nucleotide polymorphisms, or SNPs, located on four other chromosomes. SNPs are naturally occurring spots in the DNA where some people have one DNA base, or letter, and other people have another. variants didn’t change any genes, but were found near some ‘ that may be involved.

For instance, a variant on chromosome 15 linked to men having sex with men is also associated with male pattern baldness.例如，与男性发生性关系有关的15号染色体上的一个变体也与男性秃顶有关。 Another variant in the study is near the ORA51A gene on chromosome 11, which is involved in the ability to smell certain chemicals. That’s interesting because smell has been linked to attraction before (SN Online: 3/12/15), Ganna said. The researchers don’t yet know exactly which genes are involved in mate choice or exactly how they influence behavior.

One mystery the discovery may help solve is how genetic variants associated with having same-sex partners could persist across generations.这一发现可能有助于解决的一个谜是，与同性伴侣有关的基因变异如何在不同的世代中持续存在 Such variants would presumably get weeded out if men and women who have sex with people of the same sex don’t have children or have fewer children than the average person.如果与同性发生性行为的男性和女性没有孩子，或者比普通人生育的孩子少，那么这种基因变体可能会被淘汰。

In the new study, the more exclusively homosexual partners men had, the fewer children they had; up to 80 percent fewer children than heterosexual men.在新的研究中，男同性恋伴侣越多，他们的孩子就越少;孩子比异性恋男性少80%。 In a preliminary conference report, the researchers suggested that the variants are associated with heterosexuals having more sexual partners than usual, and that heterosexual men with some of the variants are more attractive than those without. 这种变异与异性恋者拥有比通常更多的性伴侣有关，而带有某些变异的异性恋男性比没有变异的异性恋男性更具吸引力。Those traits would give heterosexuals a greater chance to pass the variants on to offspring, keeping those DNA differences in the gene pool. Ganna did not discuss those possibilities from the podium.

Diamond disagrees that researchers need to find a mechanism to explain the persistence of genetic variants linked to homosexuality.戴蒙德不同意研究人员需要找到一种机制来解释与同性恋有关的遗传变异的持续存在 Same-sex behavior has never completely supplanted heterosexual mating in any species studied, she says. Only in the last 50 years have gay people tended to exclusively choose same-sex partners, she says. “You don’t really need some reproductive benefit for same-sex sexuality, because same-sex sexuality almost never occurs exclusively. 你真的不需要同性性行为带来生殖方面的好处，因为同性性行为几乎从来不会只发生在你身上。Individuals with that predisposition have been mating and reproducing with heterosexual partners for millennia, and that’s why it’s still in the gene pool.”具有这种倾向的个体已经与异性伴侣交配繁殖了几千年，这就是为什么它仍然存在于基因库中的原因

Citations

A. Ganna et al. Large genome-wide analysis of sexual orientation identifies for the first time variants associated with non-heterosexual behavior and reveals overlap with heterosexual reproductive traits. American Society of Human Genetics annual meeting, October 19, 2018, San Diego.