XV Harry Benjamin International Gender Dysphoria Association Symposium

The State of Our Art and the State of Our Science

The genetic origin of Asexuality, Homosexuality, Transvestism, and Transsexuality

By William J Turner MD
Department of Psychiatry, University of New Mexico, Albuquerque, NM 87110, USA
Abstract

Clinical study of asexuality, transvestism, homosexuality, and transsexuality reveals that some ninety-five percent of these gender variations are maternally transmitted. The maternal uncle/aunt ratio is nearly identical for each condition. Each and all of these conditions may occur together not only within extended kinships, but also among sibships as well as in monozygotic twins. It is proposed that there is a default gene for gender, designated G-G, located in the Xq28 region of the human genome. Default action of this gene is thought to result in heterosexuality; interference with it to result in gender variations. Following the example of Fragile X mental retardation, the non-Mendelian familial pattern of these conditions is thought to depend upon influence of trinucleotide repeats upstream to G-G. The mechanisms for gender variants among women may depend also on methylation of cytosines of trinucleotide repeats, maternal imprinting, or mutations in G-G.