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Does A Gay Gene exist? Two possible ways the genetic material for homosexuality may be transmitted J. Michael Bailey of Northwestern U. and Richard C. Pillard of Boston U.
did a study on 161 gay men. Each had at least one identical twin or fraternal twin or adopted brother. Fifty two percent of the identical twins were also homosexual, as compared with twenty two percent of the fraternal twins and eleven percent of the adopted brothers. Similar studies have been done by Dean Hammer and others with the same results. If one of the identical twins is gay, then there is over a fifty- percent likely hood that the other will also be gay. This is strong evidence that homosexuality has at least a partial basis of inheritance.
Thus, a search began to find the gay gene (s). Dean hammer noted that a seemingly high number of homosexual men that he studied had gay uncles on their mother s side. He speculated that the gay gene (s) might be located on the X chromosome. Hammer examined X-chromosomes of gay men, trying to find any differences with the X-chromosomes of heterosexual men.
In the region Xq 28, he found a pattern that was common to many homosexuals. Two thirds of the gay men that he tested had that pattern. That would explain the reoccurrence of the gene despite its negative selection (homosexuals tend not to have children). Since males have only one X chromosome (compared with females who have two), the genes on the chromosome are more likely to be expressed. Hence, a man with the Xq 28 has a greater chance of being gay. As for women, presence of Xq 28 does not seem to affect sexual preference.
That may be due to their extra X or that the genes simply might not express themselves the same way in women. Thus, normal heterosexual women can pass the gene down through successive generations. Other scientists like Richard C. Pillard and J. Michael Bailey have a different opinion. They believe that dozens or hundreds dozens or hundreds of alleles are related to sexual attraction.
That believe homosexuality can be inherited genetically but do not claim to know the specific genes responsible. They speak of possible selective advantages of the kin of homosexuals. In their words if alleles persist for a condition that is reproductively deleterious in the homozygote, then there must be a selective advantage for the heterozygote. The hypothetical advantage need not have anything to do with sexual attraction. It could involve genes of other attributes. An example would be resistance to endemic disease.
That would promote a larger sibship (thereby offsetting the phenotypically gay individual). Another example would be personality traits associated with gay genes. A trait like that would improve hunting skills is a good example. It would make up for the genetic loss if these traits increase the survival rate often. These scientists say that even if the selective advantage were small (less than 2 %) it would be sufficient to balance the affect of the loss of fertility of the homozygote.
The two theories that I have discussed are valid explanations of how the gene could be passed on consistently from generation to generation consistently. Perhaps much more valid than if they were to stand on their own. I feel necessary to discuss some of the weak points of these theories. To believe in these theories, you must believe in genetic determinism. Many people do not. They believe that environmental factors determine sexual orientation.
They would argue that a social behavior as complex as homosexuality cant be governed by a couple of genes. The theories themselves have been barely surviving continued attack of the scientists. Many have already claimed the many gay men who do not have the Xq 28 pattern? Many have claimed to have disproved Xq 28 theory.
Many questions remain. How do you account for Homosexuals who dont have it? Alternatively, How do you account for heterosexuals who have it? A Canadian study said that there was no significant difference between maternal and paternal uncles being gay. As for the second theory I discussed, the weakness is that it is almost impossible to pinpoint the exact genes that determine sexual orientation. The current theories are not convincing.
Twin studies provide strong evidence of a genetic factor in homosexuality. If there is a genetic factor, then we are very far from knowing what the genes are, and how they are transmitted. Scientists must continue searching for a gay gene (s). It will be tough and probably near impossible to come up with a complete answer.
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