"Gay gene?" What revealed the largest DNA study in history

Like being big or small, whether you like men or women It is not defined by a single gene, but by several regions of the genome and, like any complex human feature, by multiple non-genetic factors.

This is the conclusion of an badysis carried out in half a million profiles of DNA by a group of researchers from Europe and the United States, published Thursday by the prestigious magazine Scientific Magazine. The study aims to bury the idea that emerged in 1990 that there is a "gay gene".

"It's actually impossible to predict badual orientation Ben Neale, a member of Harvard Broad Institute and MIT, one of the many institutions from which the authors come.

The researchers say that badual orientation has a genetic component, confirming smaller earlier studies, especially in twins.

But this component depends on a large number of genes. "There is no single gay gene, but many small genetic effects spread throughout the genome, "says Neale.

Added to this is an essential factor: surroundings in which a person grows up and lives.

To better explain, researchers compare it to the size of a person. The genetic effect is indisputable.since the bearing is linked to that of the parents. But genetics does not explain everything: nutrition during childhood will have a significant impact. This is what scientists call environment.

The same goes for heart risk: genes create predispositionsbut lifestyle and diet play a bigger role.

Limited influence

The new statistical badysis revealed five precise positions in our chromosomescalled locus, which appear to be clearly related to badual orientation, although each has a "very weak" influence.

Biologically, it turns out that one genetic marker It is also badociated with hair loss, suggesting a link with the regulation of bad hormones.

Presumably, there are hundreds or thousands of other markers that future badyzes in larger DNA banks might discover someday.

"It's a complex behavior where Genetics plays a rolebut probably a minority. The effect of the environment exists, but we can not measure it exactly, "says Fah Sathirapongsasuti, a scientist at 23andme.com, a DNA test site that contributed to the study with genetic profiles of voluntary clients.

Most of the badyzes were done on men and women from the UK-based UK Biobank, mainly of European origin, who answered the question: Have you ever had bad with a person of the same bad?

The complexity

The authors are aware of the delicacy of the subject. Two of the researchers took care to remember that they were themselves homobaduals.

To avoid misinterpretation, they consulted LGBT badociations on how to communicate the results, which they summarized on a website. genebadbadhavment.info, in English.

The American badociation GLAAD praised the research confirming that "Being gay or bad is a natural part of human life".

In 1993, a study of 40 families thought they had identified a unique place, the Xq28 genewhich defines badual orientation. The new badysis refutes this simplistic model.

It is likely that a figure revealed by this study creates confusion. Researchers estimate that "8 to 25%" of differences in badual orientation in the test population, they are due to genetic variations.

But this figure is a statistical concept about a population and does not mean that 25% of a person's orientation depends on his genes.

Another result puts at risk the idea that badual orientation can be measured in a range, according to the so-called Kinsey scale, named after the American biologist who defined it in 1948.

This scale is divided into degrees: from 100% homobadual to 100% heterobadual, to bibadual.

"Assuming that the more you are attracted to a person of the same bad, the less you are attracted to the other bad, it is an oversimplification," said the researchers, after comparing the genetic markers that affect the number of partners of each bad.