An algorithm using epigenetic information from just nine regions of the human genome can predict the sexual orientation of males with up to 70 percent accuracy, according to research presented on Thursday, October 8, at the American Society of Human Genetics (ASHG) 2015 Annual Meeting in Baltimore, Maryland. “To our knowledge, this is the first example of a predictive model for sexual orientation based on molecular markers,” said Tuck C. Ngun, Ph.D., first author on the study and a postdoctoral researcher at the David Geffen School of Medicine of the University of California, Los Angeles (UCLA). The title of Dr. Ngun’s ASHG abstract is “A Novel Predictive Model of Sexual Orientation Using Epigenetic Markers.” Beyond the genetic information contained in DNA, the researchers examined patterns of DNA methylation – a molecular modification to DNA that affects when and how strongly a gene is expressed – across the genome in pairs of identical male twins. 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. In all, the study involved 37 pairs of twins in which one twin was homosexual and the other was heterosexual, and 10 pairs in which both twins were homosexual. “A challenge was that because we studied twins, their DNA methylation patterns were highly correlated,” Dr. Ngun explained. Even after some initial analysis, the researchers were left with over 400,000 data points to sort through.
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