Genetic code 70% accurate

An LGBT activist gets ready in front of a rainbow colour flag during the Rainbow Pride Rally in Kolkata, India.

An LGBT activist gets ready in front of a rainbow colour flag during the Rainbow Pride Rally in Kolkata, India.

Published Oct 9, 2015

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Scientists claim they can predict whether someone is gay or straight with a 70 per cent accuracy by looking at their DNA.

It has long been believed that sexuality has a biological basis, with certain genes linked to being gay.

But the claim that sexual behaviour can be predicted to such a high degree was described as ‘bold’ by British scientists yesterday.

The discovery does not mean scientists could predict the sexuality of a child before it is born, because the tests were carried out on adults.

But by pinpointing parts of genes that seem to have a role in deciding whether someone is gay or straight, it could conceivably be a step towards such a test. Any such test would be controversial because it would raise the possibility that scientists could try to decide the future sexuality of ‘designer babies’.

While our genes are determined at birth, tags on the genes that affect how they work can change over time because of factors in the environment or in the womb.

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

Identical twins usually, but not always, have the same sexuality. This finding has led scientists to believe there is a genetic component to being gay. To pinpoint this, Dr Ngun and his team studied the genes of 47 pairs of adult male identical twins – 37 pairs in which one brother was homosexual and the other heterosexual, and ten pairs in which both were homosexual.

They found that nine small regions of the genetic code play the key role in deciding whether someone is heterosexual or homosexual.

The research looked at a process called methylation of the DNA, which has been compared to a switch on the DNA making it have a stronger or weaker effect. This process can be triggered by hormonal effects on the growing foetus.

While identical twins have exactly the same genetic sequence, environmental factors lead to differences in how their DNA is methylated. Thus, by studying twins, the researchers could control for genetic differences and tease out the effect of methylation. This alteration of the gene is known as an ‘epigenetic’ effect.

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

Commenting on the research, Darren Griffin, professor of genetics at Kent University, said: ‘To claim a 70 per cent 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.’

Professor Tim Spector from King’s College London, a leading expert on twin studies and genetics, said: ‘The small study needs replicating before any talk of prediction is realistic.’

 

© Daily Mail

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