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 on the Xq28 portion of the X-chromosomes. In this region of the X-chromosome there are 5 distinctive gene markers. The markers on this section of the X-chromosome for many of the homosexual men had surprising similarities. This data of such close affinity was then run through a series of genetical computer programs. Once finished reviewing the data, the computer supported a close junction between the Xq28 gene and homosexuality. The study looked at all of the regions on the X-chromosome, not just the Xq28 region, and no conclusive evidence showed any relation between any other section and homosexuality (Hamer,Hu,Magnuson&Patatucci, 1993). Most of the information concerning the link between genetics and human sexual orientation was on the male perspective of this only.
Another study has been underway for some time, dealing with the genetic aspects of sexual orientation in fruit flies. This does not directly pertain to the human portion of this study, but it may demonstrate that a sexually defining gene is a possibility. Work accomplished at Stanford University, along with many other universities, have discovered a gene that inhibits the male fruit fly from distinguishing between the sex of other fruit flies. Therefor a male fruit fly whom cannot distinguish between male and female may appear to have homosexual tendencies, but this to would also be partially determined by
other factors (Stover, 1997). Fruit flies are very basic organisms when compared to humans and although this finding does not actually support the theory of genetic human
sexual orientation, it definitely does shed some light of hope that a specific gene may be found in humans.
Research into the origins of homosexuality has gone back to times where there was no genetic involvement. These studies included looking at such things as amount of facial hair, and the size and shape of genitalia. However, today genetics is a very serious subject that many people would rather just see left alone. There are many moral and ethical concerns surrounding this controversial subject, and there are many scientists and researchers who would like to disclaim the newborn evidence. One of the main ethical concerns is further and more escalated discrimination against an already submissive homosexual population. Another, is the fact that if a ?gay gene? is found, parents will be able to determine the sexual orientation of their child through in-utero testing. This would cause an increase in the gay community to only want homosexual children and an increase in the straight community to only want straight children (Schuklenk&Stein, 1997). Many people believe however, that a genetic link to sexual orientation would reduce homosexual discrimination. Although today in our society people are discriminated against on the basis of the color of their skin or their religious beliefs. Another hope in finding a genetic link involves the lifting of certain bans and laws, currently governing some of the activities of homosexuals. A link to genetics would also give the lesbian and gay community a defense against the prejudice people of this country, and countries around the world.
The Hamer study supported a theory that there may be a possibility of traits passed down through the genes of mothers that determine a linkage between genetics and human sexual orientation. The fact still remains that much more testing is in order to fully determine the sequence of the human genome in general, not to mention specific genes relating to one specific category, such as human sexual orientation.