Scientists Claim They Found 'Gay' Gene Changes to Predict Sexuality

Researchers from the David Geffen School of Medicine of the University of California, Los Angeles, said they can determine someone's sexuality by looking at specific changes in genes, NBC News reports.

The details of the research have not been made public, but the information has been presented at a meeting of genetics experts. The data suggests there are a number of factors that come together to determine if someone is homosexual or heterosexual.

"To our knowledge, this is the first example of a predictive model for sexual orientation based on molecular markers," Tuck Ngun, a researcher at the David Geffen School of Medicine of the University of California, Los Angeles, who led the study, told NBC News.

NBC News reporters critics say Ngun's study group was too small to know for sure if his research is valid, however.

At a meeting in Baltimore, Md., with the American Society of Human Genetics, Ngun said he looked at epigenetic changes called methylation in 47 pairs of male twins. Identical twins have the same DNA but epigenetic changes, or genetic changes that are made during life and are not handed down from parents, can impact someone later in life.

Based off these changes, Ngun said he and his team of researchers created an algorithm that determined if someone is gay or straight.

"Sexual attraction is such a fundamental part of life, but it's not something we know a lot about at the genetic and molecular level. I hope that this research helps us understand ourselves better and why we are the way we are," Ngun said.

Other researchers said Ngun's idea would have to be tested on many more people, however.

"Without validation of the result in an independent data set it is not really possible to know whether there is any substance in this claim," Gil McVean, a statistical geneticist at Britain's University of Oxford, told NBC News.

"My gut feeling it that, as the complete story unfolds, the association may not be quite as simple as the summary (abstract) and press release suggest. The important thing to note however is the mounting evidence that homosexuality is a perfectly normal trait segregating in human populations," genetics professor Darren Griffin of the University of Kent said.

Dr. Margaret McCarthy, who studies the developing brain at the University of Maryland School of Medicine, said looking at epigenetic changes could occur while the fetus is developing.

"Developing male fetuses produce very high quantities of testosterone during the second trimester and this directs psychosexual development along masculine lines, a component of which is preference for females as sexual partners," McCarthy said in a statement.

"This study provides a major step forward in our understanding of how the brain can be affected by factors outside of the genome," she said. "It is also possible that the experience of being a homosexual or a heterosexual has itself impacted the epigenetic profile. But regardless of when, or even how, these epigenetic changes occur, their findings demonstrate a biological basis to partner preference."