I saw this at
http://abcnews.go.com/sections/living/DailyNews/gaygene990422.html

Biological Links to Homosexuality

1991: Northwestern University's Michael Bailey and others find greater homosexual correlation among identical twins than fraternal.
1991: Salk Institute’s Simon LeVay discovers that a tiny section of the hypothalamus in the brain is smaller in gay men than in straight men.
1992: Laura Allen and Richard Gorski of the University of California at Los Angeles discover that a section of the fibers connecting the right and left hemispheres of the brain is one-third larger in gay men than straight men.
1993: National Cancer Institute’s Dean Hamer study finds possible location of “gay gene” on the X chromosome, inherited from mothers.
1995: Geneticists Shang-Ding Zhang and Ward Odenwald of the National Institutes of Health discover that a single transplanted gene can cause fruit flies to display homosexual behavior.
1995: Hamer repeats his 1993 findings with a follow-up study.