A gene is a molecular unit of heredity of a living organism. In simpler terms, sections of DNA that contain complete instructions are known as genes. Since they are units of heredity, they can be passed on from one generation to the next. Genes determine which species a living organism belongs to (Arnqvist 1061). Genes usually encode for proteins. Proteins go out into the body and carry out the instructions given to them by the genes. Molecular engineering has been used to tinker with genes and to change what they code for. Sometimes these genes are removed entirely and replaced with different ones. In the long debate on homosexuality, many wonder if it is a lifestyle choice or if it is determined by one’s genes. Religious sects condemn it as evil and some even believe that prayers can ‘cure’ homosexuality. Scientists have carried out studies to try and find out if a gay gene exist and lay the debate to rest.
In his article, Burr compares human sexual orientation to human handedness. Both traits have a majority orientation and a minority orientation. People do not choose to be left-handed and there is no gene that has been found for left-handedness (Burr para. 4). If there is a gene for left-handedness, it shows a lot of variation. Some left handed people use the left hand for writing while using the right for other activities while others use the left for particular activities only (Lalumière, Blanchard and Zucker 576). If this gene existed and it was similar to a gay gene, it would explain the difference in gay people. Some gay individuals’ exhibit highly feminine characters while others seem to be just on the edge between heterosexual and homosexual. Where then would one draw the line between being gay and being straight? Discovery of a gay gene would be a very important factor in eliminating doubt.
If a gay gene is real, what would be the probability of inheriting it? In pedigree analysis, traits that are genetically influenced aggregate in families and in the case of dominant or sex-linked inheritance, are transmitted from one generation to the next (Dean 322). Since males receive the X chromosome from their mothers, if the X chromosomes contain a gene that increases the probability of being homosexual, then there would be a higher incidence of homosexuality in brothers. Human sexuality is complex and there is no single genetic locus that has been found to account for homosexuality (Dean et al. 323).
Some scientists argue that it is not the presence of a gay gene but the absence of certain genes that causes homosexuality. There are certain proteins that control sex orientation in mice. A good example is an enzyme known as fucose mutarotase whose absence in mice was proven to cause an abnormal sexual receptivity. This is according to research carried out by Dongkyu et al (2). They were able to observe that mice lacking in the above enzyme could not utilize and incorporate fucose into protein. This led to masculine behavior and a preference for female urine. In a different study by Yan et al (para. 4), the neurotransmitter 5-hydroxytryptamine was discovered as being a requirement for male sexual preference. Previous studies have implicated this neurotransmitter in male sexual behavior but not in sexual preference (Yan et al para. 5). Certain mutations are a biological explanation for sex orientation. In a study by Kimchi et al (4), it is reported that Trpc2 female mice show a reduction in female-specific behavior. These mutant females are said to have displayed unique characteristics of male sexual and courtship behaviors like mounting, pelvic thrust, solicitation and anogenital olfactory investigation. In mice, pheromone detection is mediated by the vomeronasal organ (VNO) and the main olfactory epithelium. Male mice that are deficient for TRPC2, an ion channel specifically expressed in VNO neurons and essential for VNO sensory transduction, are impaired in sex discrimination and male-male aggression (Kimchi et al.). Other studies show that there are rare alleles encoding either male ornaments or female preferences for them that are better protected against loss in species (Hudson and Pfenning 1090). In this study, they argue that in evolution, mutation may lead to males evolving elaborate secondary sexual traits as seen in some animals.
Hormones may also play a role in sexual orientation. Right after conception, it is hard to tell male and female zygotes apart. The female brain is the default. The ‘masculinisation’ of the male brain by sex hormones initiates sex changes (Swidey para. 4). The theory of how hormones affect male sexual orientation is based on this fact. If the brain develops as female in the absence of testosterone, what leads to the loss of female characteristics leading to lesbianism? Research in mammals has demonstrated that pheromone sensing in the periphery is important for sexual preference. Pinker (3) differs with this finding stating that when people check out a prospective partner, they seek out words or pictures, not dirty laundry.
Scientists have studied mice behavior and anatomy to try and discover the gay gene. There are various ways that homosexual mice differ from heterosexual mice in anatomy. Mice lacking the fucose mutarotase enzyme exhibit male-like sexual behavior. This has been attributed to neurodevelopmental changes in the preoptic area of the mutant brain resembling a wild type male (Dongkyu et al 2). Males lacking central serotonergic neurons lost sexual preference (Yan et al. para. 8).
Reproductive behaviors (for example, receptivity or mounting) are one of the characteristics of sexual differences. Mice are usually the animal of choice in experiments because they are mammals and reproduce fast. They are more ethically acceptable than primates and are genetically similar to humans. On the other hand, there is a difference between specific hormones in mice and those found in human beings (Liu para. 5). As such, studies carried out on mice may not entirely be compatible with those carried out on human beings.
What would happen if a gay gene in humans was discovered in humans? If this happened, there would be a great change in the way gay people are perceived and treated. There would be a reduction in homophobic behavior since being gay would not be regarded as an option anymore (Swidley para. 7). Most believe that a gay gene would go against the theory of evolution. Natural selection is based on the fact that the best traits are passed on and persist in order to keep the species alive. The gay gene, if there was one, would not lead to reproduction and would lead to the dwindling of the human species. In this case, nature may have found a way of reducing human population in a less gruesome way like floods, famine and disease in the past.
There would be disadvantages too in that some mothers would probably opt to change their child’s sexuality or to abort a child with this gene. The presence of a gay gene in people who believe they are heterosexual would also likely cause confusion. It may also lead to discrimination because it would be possible for an organization to determine one’s sexual preference scientifically. Religious sects would have to come up with a way to accept gay people, not as sinners, but as a creation of God which would go against most popular religious teachings.
Works Cited
Arnqvist, Goran, Edvardson, Martin, Friberg, Urban and Nilsson, Tina. “Sexual Conflict Promotes Speciation in Insects.” Proc Natl Acad Sci, 97(2000): 10460-10464
Burr, Chandler. “The “Gay Gene” Hits the Big Time”. The Harvard Gay & Lesbian Review. 26.1996
Dean H. Hamer, Stella Hu, Victoria L. Magnuson, Nan Hu, Angela M. L. Pattatucci. “A Linkage Between DNA Markers on the X Chromosome and Male Sexual Orientation.” Science, Science 261. 5119 (1993): 321–7
Dongkyu, Park, Dongwook, Choi, Junghoon, Lee, Dae-sik. Lim and Chankyu, Park. “Male—like sexual behavior of female mouse lacking fucose mutarotase.” BMC Genetics, 11.62 (2010):1-2
Hudson Kern Reeve and David W Pfenning. “Genetic Biases for showy males: Are some genetic systems especially conducive to sexual selection?” PNAS, 100 (2003):1089-1094
Kimchi, Tali, Jennings, Xu and Dulac, Catherine. “A functional circuit underlying male sexual behavior in the female mouse brain.” Nature 95.472 (2011)
Lalumière, Martin, Blanchard, Ray and Zucker, Kenneth. “Sexual orientation and handedness in men and women: a meta-analysis”. Psychol Bull, 126. 4(2000): 575–92.
Pinker, Steven. “Sniffing Out the Gay Gene.” Boston Globe, 2005. Web.
Swidey, Neil. “What Makes People Gay?” Boston Globe, 2011 Web.
Yan, Liu, Jiang Yun’ai, Si Yunxia, Kim Ji-Young,Chen Zhou-Feng and Rao Yi. “Molecular regulation of sexual preference revealed by genetic studies of 5H-T in the brains of male mice.” Nature, 10.1038 (2011).