Recent Developments in Research on the Genetics of Human Sexual Orientation

Recent Developments in Research on the Genetics of Human Sexual Orientation

Human sexual orientation has been a controversy with a high tendency for debate. Lesbians, gays, supporters, and their friends are in a heated dispute about the origins of sexual orientation. There are many possibilities, spanning from personal lifestyle choices, environmental factors, to genetic heredity.

In the past few years it has become increasingly popular to examine homosexuals, in hopes of determining the basis for a lifestyle involving same sex relationships. Henry Havelock Ellis first addressed inquiries on the basis of homosexuality over a century ago. Ellis stated that people engaging in sexual practices deviating from the regular format should be accepted by society, and laws against this group of people should be put aside, due to the biological differences of each persons makeup (Hyde & DeLamater, 1997). Most of the recent discussions and studies on homosexuality with a genetic influence have begun in the past decade.

Many researchers of this decade have been involved in the discovery of a "gay gene", but none as much as the infamous Dean Hamer (Pool, 1997). Hamer studied under molecular biology and psychology, so there is no concrete title by which he goes. Hamer spends his days searching countless thousands of human genes and genes of other species in what seems like an endless investigation into what shapes our human personalities. "I believe we'll find out something important about human behavior by studying its genetic basis," says Hamer. Dean Hamer never insists however that genetics

rules every aspect of our personalities. He simply says that genetics does play a role in forming certain traits, coupled with home environments, schools of attendance, ethnic backgrounds and factors such as these. When looking at genetics from this perspective the previous elements are called shared environmental factors, and do have significant influence on personally inherited traits.

Hamer has been involved in many other scientific avenues, such as cancer and AIDS research. In fact he began his search for the "gay gene" while he was looking at a correlation between a fatal cancer and why it effects so many homosexual AIDS patients. Many influential findings have come from Hamer's research, but none as controversial as the one which he says links male homosexuality with a series of genes on the X-chromosome (Pool, 1997). The experiments conducted by Hamer are still ongoing today, and probably will not be finished until thousands of test subjects are put through the necessary steps to discover the elusive "gay gene."

Openly gay men gave informed consent along with their relatives that were 18 years of age or older. The procedure consists of giving blood, to be thoroughly examined for certain matching characteristics on each subjects DNA. Following this, each member of the study is asked to complete a number of questionnaires and interviews to determine their shared environmental factors, as mentioned earlier. Much more detailed looks at shared environmental factors take place in this study, including mental health history, HIV status, and alcohol and substance abuse (Hamer,Hu,Magnuson&Pattatucci, 1993).

At the end of each strand of male DNA there is a specific X-chromosome that is obtained from the mother of the individual and a Y-chromosome which comes only from the father. While looking at the similarities between father, son, and homosexuality, it was determined by the team that if homosexuality was a specific genetic trait, it most probably was passed through the mother of the subject. This in turn determines that if the X-chromosome is responsible for passing the trait of homosexuality then related gay men should have a specific gene or chromosome marker which indicates their sexual orientation (Hamer,Hu,Magnuson,&Pattatucci, 1993).

Hamer and colleagues performed an X-chromosome linkage on several pairs of homosexual brothers. The reason for using brothers is the obvious relationship of each individual DNA structure, and the ability to recognize even slight differences on each genome. Mistakes in comparing genotypes of brothers are uncommon. The mothers and siblings, if any were available, also had DNA samples prepped for examination, to view similarities of markers that run up and down the X-chromosome. Again to narrow the search for the specific gene, only the brothers who had the same X allele from their mothers (which was the majority) were continually looked at (Hamer,Hu,Magnuson,&Pattatucci, 1993).

When looking for chromosome markers, series of repeated genes are looked over. A chromosome marker occurs when a break in gene sequence is spotted. Usually some problems arise when comparing DNA of separate individuals, but during this study of mothers, sons, and siblings, the individual alleles were easily differentiated. Almost all

of the subjects studied obtained their X-chromosome from their mother and their Y-chromosome from their father. Once the genotypes were identified from each individual

involved in the study, and their mothers, the genotypes were compared for similar marker placement with the samples from the other family groups. The most significant finding when doing this study, were the similarities