The DNA Rainbow: GeneSoc to feature the Genetic Realm of the Gender Spectrum

By: Sean Lemuel L. Santos (Hybrizyme)

RAINBOW IN THE DNA | An artist's sketch of the DNA--the molecule which holds the secrets to the genetic basis of gender and human sexuality. Image taken from: Getty Images 

The UPLB Genetics Society will illuminate the minds of the youth as they feature the genetic basis of gender through a rainbow-filled exhibit and week-long activities on April 9-13, with the theme, “Beyond Binary: Exploring the Genetic Realm of the Gender Spectrum”.

----

Gender, defined as “the socially constructed characteristics of men and women” by the World Health Organization, is a fundamental aspect of an individual. It affects how a person thinks, acts, would establish relationships, would express one’s self, and many others. As revealed by findings in genetics, gender is now understood as something that is influenced by our genes, as well as by the environment which could be sociological, psychological or physiological. This understanding provides us an additional, scientific perspective in viewing gender as an essential facet that defines us as a human. Here, we will be exploring the genetic links to the categories associated with gender such as biological sex, gender identity and gender expression, as well as sexual orientation. These categories are based on “The Genderbread Person” which provides us a clear illustration of the gender spectrum.

Biological Sex

Biological sex is based on a person’s chromosomes, specific genes, hormones and sex organs. Generally, in humans, females have two X chromosomes while males have an X and a Y chromosome. The two X’s in a female are inherited both from her parents. But in the case of the male, only the father can give the Y chromosome while the mother gives the X. In the Y chromosome, there is a gene called SRY (referring to sex-determining region in Y) which codes for hormones that activate the formation of male sex organs. In contrast, females do not have a Y and therefore lacks SRY gene which leads to the formation, instead, of female sex organs. However, there are cases when a person is considered as an intersex, wherein his/her internal and external genitalia are inconsistent (i.e. male-internal, female-external). Medical disorders such as congenital adrenal hyperplasia, androgen insensitivity syndrome and 5-alpha reductase deficiency cause a person to be intersex.

Gender Identity

Gender identity is how you view your own gender. Several researches have suggested possible links to genetics and gender identity. In a 2003 study conducted by researchers in the University of California at Los Angeles involving mice embryos, it was found out that there are a total of 54 genes which have different activity levels in the mice brain depending on gender. In the 10-day old embryonic mice (days prior to the emergence of sex organs), they discovered that 18 genes were more active in the male embryonic brains while 36 genes showed higher activity in the female embryonic brains. In another study conducted by Hare and other researchers in 2009, it was shown that there is a considerable link between transsexualism (having a gender identity of the opposite sex) and the AR (Androgen Receptor) allele. The results showed that transsexual males have a longer AR repeat lengths than non-transsexual males. The researchers explained that a longer repeat in the AR allele lessens the binding of the AR protein to its-coactivator which reduces testosterone signaling. This then leads to incomplete brain masculinization and the manifestation of a female gender identity in transsexual males.

Gender Expression

Gender expression is how you show your gender through your manners, actions, clothing style, etc. Toy-preference tests involving children are commonly done in genetic studies to examine gender expression. Accordingly, the toy a child prefers would indicate his/her gender expression. Playing with a car would show maleness and playing with a doll would exhibit femaleness. It is believed that there are more boys than girls who prefer cars and more girls than boys who prefer dolls because they were parentally guided to play with those toys. However, a 2002 paper published in Evolution and Human Behavior reveals that the same toy preference is exhibited in monkeys – that is, without parental influence. The researchers have observed that male monkeys tend to prefer toys that exhibit movement while females play with toys that exhibit ‘nurturance’. They explained that toy-preference among male and female primates may have been a consequence of evolution and is therefore influenced by genes which were favored in different sexes. The study, however, pointed out that gender socialization can also steer object preference.  

Sexual Orientation

Sexual orientation is based on whom you are attracted to. It can be broken down into two sub-categories: sexual attraction (the want for a sexual relationship) and romantic attraction (the want for an emotional relationship). In 1993, Dean Hamer and his colleagues pointed out that in the majority of male individuals, a locus in the q28 region of the X chromosome could be influencing male sexual orientation. How did they arrive at this conclusion? First, they found out in their study that a homosexual male had more homosexual relatives in the mother side than in the father side. This means that the locus they are looking for is more likely in the X-chromosome. Then, they noticed that the sharing of Xq28 allele is higher homosexual male siblings. This led them to associate the Xq28 allele with male sexual orientation.

While aspects in gender can be understood in the genetic perspective, it is important to realize that gender is not influenced solely by genetics. There are other environmental factors that could influence gender such as the individual’s sociocultural atmosphere, hormones, brain wiring, and many others. Furthermore, research findings linking genetics and gender ought not to be ascertained as settled facts. Genetic research about gender is still in its infancy and the knowledge about its genetic basis is still expanding. Nonetheless, these researches are shedding new light and are widening our understanding on how our genes influence our gender and sexuality. These emerging studies truly attest that gender is beyond binary as revealed by the genes that we possess.

----

The BIO 30 Week will have the following activities: Exhibit Opening and GENEWS Launching, Genetics Quiz Contest, Print-All-You-Can and 3^rd BIO 30 Tutorials.

References:

Alexander, G. M., & Hines, M. (2002). Sex differences in response to children's toys in nonhuman primates (Cercopithecus aethiops sabaeus). Evolution and Human Behavior, 467-479.

Hamer, D. H. (1999). Genetics and Male Sexual Orientation. Science, 803.

Hare, L., Bernard, P., Sánchez, F. J., Baird, P. N., Vilain, E., Kennedy, T., & Harley, V. R. (2009). Androgen Receptor Repeat Length Polymorphism Associated with Male-to-Female Transsexualism. Biological Psychiatry, 93-96.

Killerman, S. (2017). A Guide to Gender: The Social Justice Advocate's Handbook (2nd ed.). Austin, TX: Impetus Books.

Lewis, R. (2010). Human Genetics (9th ed.). New York, NY: McGraw-HIll.

University Of California Los Angeles. (2003, October 22). Brain May 'Hard-Wire' Sexuality Before Birth. Retrieved from ScienceDaily: https://www.sciencedaily.com/releases/2003/10/031022062408.htm

World Health Organization. (2018). Gender, equity and human rights. Retrieved from World Health Organization: http://www.who.int/gender-equity-rights/understanding/gender-definition/en/