By using epigenetic information from just nine regions of the human genome, a new algorithm can predict the sexual orientation of males with up to 70 percent accuracy.
“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.
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. “The high correlation and large data set made it difficult to identify differences between twins, determine which ones were relevant to sexual orientation, and determine which of those could be used predictively,” he added.
To sort through this data set, Dr. Ngun and his colleagues devised a machine learning algorithm called FuzzyForest. They found that methylation patterns in nine small regions, scattered across the genome, could be used to predict study participants’ sexual orientation with 70 percent accuracy.
“Previous studies had identified broader regions of chromosomes that were involved in sexual orientation, but we were able to define these areas down to the base pair level with our approach,” Dr. Ngun said. He noted that it will take additional research to explain how DNA methylation in those regions may be related to sexual orientation. The researchers are currently testing the algorithm’s accuracy in a more general population of men.
“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,” Dr. Ngun said.
Reference: “Epigenetic ‘tags’ linked to homosexuality in men” by Sara Reardon, 8 October 2015, Nature.
DOI: 10.1038/nature.2015.18530
Ngun TC et al. (2015 Oct 8). Abstract: A novel predictive model of sexual orientation using epigenetic markers. Presented at American Society of Human Genetics 2015 Annual Meeting. Baltimore, Maryland
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1 Comment
Xi the inactive part of X chromosome pair in the egg of a woman may also play with the epigenetic behavior. The methylation of woman’s gene may play with the hereditary nature of woman giving birth to girl child predominantly. The inactive diminutive Xi also called the barr body in the egg, may assume the role of destroying the Y chromosome of the male entering the egg predominantly, resulting in only the X chromosome being successful. Only those champion Y chromosomes in the race of targeting the egg may survive. We can notice such trend in some families where girl babies are more in multiple generations. The non-methylation of chromosome in the egg, may produce normal statistics in the birth of boys and girls. The epigenetics also play an important role in LGBT behavior of the children, including homosexuality. Epigenetics is the branch of science is needed for a thorough study in future to rule out all the above doubts. Thank You.