Straight Or Gay? Sexuality Linked To DNA - Claim

Scientists in the US claim they may have discovered how to predict a person's sexual orientation.

They found nine parts of a person’s genetic code which may play a role in determining whether someone is straight or gay.

The scientists uncovered the link after comparing the DNA of 47 pairs of male twins, including brothers with different sexual orientation.

By studying molecular data from the nine genome sites, the team claim they were able to guess whether a twin pair was heterosexual or homosexual with 70% accuracy.

Lead researcher Dr Tuck Ngun, from the University of California at Los Angeles, said: "To our knowledge, this is the first example of a predictive model for sexual orientation based on molecular markers."

He added: "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."

The research is also said to provide evidence of environmental influences affecting sexual orientation by altering the activity of certain genes.

These so-called "epigenetic" effects involve a molecular modification to DNA called methylation.

The study was presented at the American Society of Human Genetics' annual meeting in Baltimore, where many UK scientists were sceptical and said more work was needed to confirm the findings.

Professor Tim Spector, from King's College London, a leading expert on twin studies and genetics, said: "It has always been a mystery why identical twins who share all their genes can vary in homosexuality.

"Epigenetic differences are one obvious reason and this study provides evidence for this.

"However the small study needs replicating before any talk of prediction is realistic."

Darren Griffin, professor of genetics at the University of Kent, said: "To claim a 70% predictive value of something as complex as homosexuality is bold indeed.

"I wait with bated breath for a full peer-reviewed article.

"While there is strong evidence in general for a biological basis for homosexuality my personal impression has always been one of a multiple contributory factors, including life experiences."