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Big Gay might not like this …


From Nature:

Epigenetic ‘tags’ linked to homosexuality in men

The researchers collected DNA samples in saliva from 37 pairs of identical twins in which only one twin was gay, and 10 pairs in which both were gay. By scanning the twins’ epigenomes, the researchers found five epi-marks that were more common among the gay men than in their genetically identical straight brothers. An algorithm they developed based on the five epi-marks could correctly predict the sexual orientation of men in the study 67% of the time. UCLA computational geneticist Tuck Ngun will present the work on 8 October at the American Society of Human Genetics meeting in Baltimore, Maryland.

Vilain is not surprised to find that epigenetics is associated with sexual orientation, although he says it is too early to try to directly link the epi-marks to any particular environmental exposure or the expression of a specific gene. Ngun says that the researchers want to replicate the study in a different group of twins and also determine whether the same marks are more common in gay men than in straight men in a large and diverse population. Associations found in small studies are prone to evaporate when tested in larger groups. More.

The Nature editors added a note that the study has come under heavy fire.

See also: Epigenetic change: Lamarck, wake up, you’re wanted in the conference room!

Also, from the Atlantic, whose writer is not thrilled:

No, Scientists Have Not Found the ‘Gay Gene’

If you use this strategy, chances are you will find a positive result through random chance alone. Chances are some combination of methylation marks out of the original 6,000 will be significantly linked to sexual orientation, whether they genuinely affect sexual orientation or not. This is a well-known statistical problem that can be at least partly countered by running what’s called a correction for multiple testing. The team didn’t do that. (In an email to The Atlantic, Ngun denies that such a correction was necessary.)

And, “like everyone else in the history of epigenetics studies they could not resist trying to interpret the findings mechanistically,” wrote John Greally from the Albert Einstein College of Medicine in a blog post. By which he means: They gave the results an imprimatur of plausibility by noting the roles of the genes affected by the five epi-marks. One is involved in controlling immune genes that have been linked to sexual attraction. Another is involved in moving molecules along neurons. Could epi-marks on these genes influence someone’s sexual attraction? Maybe. It’s also plausible that someone’s sexual orientation influences epi-marks on these genes. Correlation, after all, does not imply causation. More.

Yes, but funny how few people think to make these critical points when evaluating studies of the fat gene, the religion gene, the infidelity gene, or the bad driving gene. Doubtless, there’ll be plenty similar stuff with epigenetics as with genetics.

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