Answers to your Questions for a Better Understand of Sexual Orientation and Homosexuality (PDF, 132KB)
Biology:
http://news.stanford.edu/pr/95/950310Arc5328.html
STANFORD -- Research into the biological basis of sexual orientation "presents a clear double message.
Yes, genetics plays a part. No, it is not all genetics," Dora B. Goldstein, professor emeritus of molecular pharmacology, told the audience that attended the first in a series of public lectures sponsored by the Medical Center's Lesbian-Gay-Bisexual Community on March 9.
"This shouldn't be too surprising because that is what all kinds of behavioral studies indicate. Genes determine everything. The environment affects everything. Then there is this big area where the two interact," she added.
In her noon presentation, Goldstein reviewed relevant research in a number of different areas: population studies, family studies, twin studies, genetic research, childhood behavior, and brain differences.
DNA studies have identified the general location of at least one "gay gene."
The maternal heritability of male homosexuality narrowed the region where such a gene must reside to the X chromosome, because sons get this chromosome from their mother. Analysis of DNA markers on the X chromosomes of sibling pairs has further narrowed the search to a region called XQ28. It consists of hundreds of genes and is located near the tip of the X chromosome. However, there is some indication that genes located elsewhere may have a similar effect on sexual orientation, Goldstein said.
Fetal development studies suggest how such a gene might influence such a complex behavior. The development of a fetus into a male is accomplished by the development of the testes, which produce testosterone, which has a wide range of physiological effects. During the perinatal period, a week before and after birth, testosterone has an irreversible organizing effect on the body and brain of males. If the hormone is absent during this period, the individual's anatomy and behavior never can become wholly male. A testosterone surge during puberty activates male sexual development and behavior.
* In 1993, the
National Institute of Health’ Dean Hamer illustrated that homosexuality might be inherited from the mother by her sons through a specific region of the X chromosome (Xq28). Hamer demonstrated this by noting that 33 out of 40 pairs of homosexual brothers whom he studied showed the same variation in the tip of the chromosome.
- Hamer DH, Hu S, Magnuson VL, Hu N. and Pattatucci AML. A linkage between DNA markers on the X chromosome and male sexual orientation. Science 1993; 261:320-326.
* A study released in May 2006 by Swedish scientists demonstrates that biology plays a key role in determining a person’ sexuality.
The research shows that the portion of the brain that helps regulate sexuality — the hypothalamus – reacted the exact same way in straight women and gay men when exposed to male pheromones, which are chemicals designed to provoke a behavior, such as sexual arousal. The same area of the brain only became stimulated in heterosexual men when introduced to female pheromones.
- by Ivanka Savic article in the Proceedings of the National Academy of Sciences, (PNAS) “Brain Response To Putative Pheromones In Homosexual Men,” (Vol. 102 No. 19) May 10, 2005.
