Researchers Find Link Between DNA Marks And Sexual Orientation

The idea that a “gay gene” exists is not without controversy, but evidence strongly suggests that sexual orientation, at least in men, is influenced largely (but not entirely) by genetics. New research is offering the first piece of evidence for an idea that has been proposed before: a link between sexual preference and DNA tags that can be influenced by the environment. This finding was presented on October 8 at the American Society of Human Genetics meeting in Baltimore.

The idea that sexuality is a choice is an archaic idea. The hypothesis that there is a genetic element to homosexuality has floated around for a while; gay twins are surely enough to prompt suspicion on the matter. But it took a long time for convincing evidence in support of this to surface. Just last year, for example, the biggest study of gay brothers to date backed up what had been proposed 20 years earlier: stretches of DNA on the X chromosome and chromosome 8 are strongly associated with sexual orientation.

It’s clearly not all down to genes, though. Studies that have looked at identical twin pairs have found that if one sibling is gay, there is roughly a 20% chance that the twin will also have the same sexual orientation. And each time a woman has a male pregnancy, the chance that her next son will be homosexual increases by 33%. These percentages clearly indicate another factor is involved.

When we talk about traits like this, the argument is often over “genetics or environment,” but what about something that is a bridge between the two? This is where epigenetics swoops in. Epigenetics refers to tags that can be added to or removed from DNA that alter the expression of a particular gene. Your DNA sequence has got to be read before proteins can be made; the tags get in the way of the scanning machinery and thus prevent expression. Imagine something getting stuck in a production line. Importantly, these can be influenced by environmental factors, but as Nature points out, they are not necessarily shared between identical twins.

Read more: http://www.iflscience.com/health-and-medicine/link-between-dna-marks-and-sexual-orientation-found-men