Genome Wide Association Study of Sexual Orientation in a Large, Web-based Cohort. E. M. Drabant, A. K. Kiefer, N. Eriksson, J. L. Mountain, U. Francke, J. Y. Tung, D. A. Hinds, C. B. Do 23andMe, Mountain View, CA.

   There is considerable variation in human sexual orientation. Heritability studies have differed on the exact scope of genetic contributions for sexual orientation, but it appears that both genetics and environment play a role. Though a few linkage studies have pointed at a possible role for certain genes on the X chromosome, the strength of that evidence is limited due to the conflicting nature of the reports and small sample sizes. We sought to clarify some of the questions surrounding the possible genetic underpinnings of sexual orientation by deploying a web-based survey to the large 23andMe database and conducting the first ever genome-wide association study (GWAS) on sexual orientation.
   We adapted the Klein Sexual Orientation Grid to examine seven elements of sexual orientation. All items were rated on a seven point scale by participants. Initial analyses focused on the self identification item as a continuous variable in response to the question How do you label, identify or think of yourself? In a sample of 7,887 men and 5,570 women, 77.2% of men 74.6% of women identified as heterosexual only, 7.3% of men and 15.3% of women as heterosexual mostly, 1.1% of men and 2.7% of women as heterosexual somewhat more, 1.3% of men and 3.5% of women as bisexual, 0.7% of men and 0.5% of women as homosexual somewhat more, 2.9% of men and 1.6% of women as homosexual mostly, and 9.5% of men and 1.8% of women as homosexual only. In both men and women, sexual identity was most significantly correlated with sexual attraction (men r=0.97, women r=0.90), sexual behavior (men r=0.95, women r=0.83), sexual fantasies (men r=.96, women r=.75), and emotional attraction (men r=0.79, women r=0.45), and the least strongly correlated with heterosexual/homosexual lifestyle (men r=.54, women r=.37), and social preference (men r=.15, women r=.08).
   We carried out GWAS stratified by sex in a cohort of 7887 unrelated men and 5570 unrelated women of European ancestry collected in the two months since the initial survey release. No clear genome-wide significant associations have been found thus far, and the current data do not show any direct association for markers within chromosome band Xq28. However, data collection is still ongoing, and increased sample size may help to clarify the roles for currently suggestive associations.

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