The research of Evelyn Hooker challenged the prevailing notion that male homosexuality was invariably associated with florid psychopathology.

Sexual orientation, whether homosexual or heterosexual, is given not chosen. A review of current literature provides a compelling body of research linking sexual orientation to genes. Male homosexual orientation has a similiar pattern of inheritance as left handedness, which means the genes for each trait are on the X chromosome. Genetics play a significantly greater role in sexual orientation than in handedness. Sexual orientation is defined as the gender one finds sexually and romantically attractive.

Of every 1,000 births about 4 are identical twins, with the same genes. Identical twins usually think of themselves as individuals, not as carbon copies of someone else, and differ in many respects. Identical twins differ for the following reasons:

1. An embryo may divide at any time up to about 14 days after conception.
2. X-chromosome inactivation (lyonization) in early female embryos randomly turns off one X-chromosome in each cell. When an embryo "twins", the halves may contain different proportions of paternal and maternal X-chromosomes.
3. "Genetic imprinting" (the process that marks which genes are be activated) in early embryos is variable.

Even though there are many human differences which have a genetic basis, such the color of our eyes, skin or hair, we are all 99.9% alike genetically.

Designer Genes

Scholarship on sexual orientation in psychology has exploded in the past two decades http://www.apa.org/monitor/apr98/sex.html

American Psychological Association has information on sexual orientation and other lesbian and gay issues. Click on http://www.apa.org/. Then click on the Search button and type in gay.

http://members.aol.com/gaygene

J. Michael Bailey and Richard Pillard, "A Genetic Study of Male Sexual Orientation," Archives of General Psychiatry 48 (December 1991): 1089-1096; Dean Hamer et al., "A Linkage Between DNA Markers on the X Chromosome and Male Sexual Orientation," Science 261 (July 16, 1993): 321-327