A genetic study that has concerned many people is the search for the "gay gene". The discovery of this gene began in the 90s and there are still questions about whether this gene exists and whether it really influences sexual orientation. Several studies have been carried out on sexual orientation through behavioral and molecular genetics. However, most of these studies have not been replicated and raise ethical concerns. Simon LeVay, a neuroscientist who has studied brain function and sexual orientation (Wikipedia contributors, 2014), published an article titled "A Difference in Hypothalamic Structure Between Heterosexuals and Heterosexuals." and homosexual men,” in 1991, which suggested a biological reasoning for sexual orientation. The hypothalamus, which is a region of the brain involved in sexual behaviors, was considered by LeVay to be a biological substrate for sexual orientation (1991). LeVay suggested that the anterior hypothalamus “participates in the regulation of typically male sexual behavior” (1991). LeVay's research indicated that there is a difference in the volume of the third interstitial nucleus of the anterior hypothalamus (INAH 3) between women, homosexual men, and heterosexual men. INAH 3 was found to be twice as important in heterosexual men as in women and homosexual men (LeVay, 1991). LeVay concluded that INAH 3 is dimorphic with sexual orientation, meaning that INAH 3 is physically different when comparing sexual orientation between groups of individuals. In 1991, a behavioral geneticist, Michael Bailey, proposed that genes may contribute to homosexuality in men (Wickelgren, 1999). Bailey found that 52% of identical male twins were homosexual, compared to 22% of fraternal twins (Wickelgren, 19...... middle of article ......o. 5119 (1993): 291- 92. JSTOR Web. March 1, 2014. Rice, William R. and Sergey Gavrilets. “Genetic Models of Homosexuality: Generating Testable Predictions.” The Ethics of Genetic Research on Sexual Orientation." Reproductive Health Questions 6.12, Sexuality (1998): 134-43. Wickelgren, Ingrid. "Discovery of the 'Gay Gene' Questioned." 284, no. 5414 (1999): 571. JSTOR Web "Wikipedia, the Free Encyclopedia. Wikipedia, the Free Encyclopedia, January 8, 2014. Web. March 1. 2014.