If you’ve been part of this world for the past few years and you’re not hiding under a rock somewhere (while I might understand that desire, I know it is impractical) you have heard of political or societal impacts of trans rights. As I was teaching genetics this year to first year high school biology classes during a pandemic I realized that the way we teach genetics in school is rife with microaggression land mines and the language we use to teach genetics could be more up to date and inclusive. As a cis/hetero female I realized that the terms used or the way questions are posed to students don’t fully encompass the lived experience any more due to medical advancements in IVF and artificial insemination or the fact that the 1950s idyllic nuclear family has never truly been representative of the lived experiences for students. Add in the growing visibility, understanding and acknowledgment of LGBTQIAA+ individuals and our genetics curriculum really needs some updating.
To begin transforming my language in the way I teach genetics I decided to delve into the genetic component and physiological expression of those genes when determining sex or gender identity. In this research what I found was an incredibly complex interplay between what the genes say you are and how they interact or are read by other code to create this balance between hardwired genetic code and the much more variable system of gene expression (in order not to bog this down too much if you’re more interested in gene expression go here).
While I’m attempting to include some of the scientific research in this field it is vastly complex, still not completely understood, and I’m just scratching the surface of the science so please seek out other more complete resources if you still have questions.
There are primary sexual characteristics which are directly related to the gonad development of a fetus and secondary sex characteristics which are things like breasts, Adam’s apples or body hair. Primary sex characteristics are generally determined by genetic composition whereas secondary sex characteristics are often determined by hormones. The genetic composition influences the hormonal release but changes in a genetic composition can dramatically affect the physical manifestation of those genes.
For a small taste of the complexities in understanding this area I just want to point out there are chromosomes such as the X and the Y that we teach and you’ve probably heard about that determine a person’s sex but the differentiation between these chromosomes being expressed involves genes like Sox9 which is found on chromosome 17; a chromosome that also contains genes that could code for colorectal and ovarian cancer as well as osteoporosis and myocardial infarction (AKA heart attack).
Sox9 is activated by the male determining factor SRY on the Y chromosome to inhibit the ovary production and actually begin the degradation of the female Müllerian duct in a chromosomal male embryo. However, it has been shown that Sox9 can create male gonads in an embryo even in the absence of SRY (AKA the Y chromosome). In essence someone may be XX but have XY primary sex characteristics.
The RSPO1 gene, located on chromosome 1 (which can code for cataracts, hypothyroidism, and migraines FYI), also plays a role in ovary determination and creation but mutations or disruptions in the RSPO1 gene can create physical males also in the absence of SRY genes and the Y chromosome.
Sox9 is considered an anti-female gene and RSPO1 is considered a female promoting gene so mutations in either of these genes or changes in time or intensity of gene expression can alter the physical appearance of the XX or XY chromosome pair.
If that hasn’t totally lost your mind that’s great! The take away though is that sex determination and gender identity are a balance between many factors and not as cut and dry as anyone would have you think. It is a constant tug of war between genes that operate to promote maleness or femaleness and genes that operate towards “anti-maleness” or “anti-femaleness” and this tug of war can create a seemingly infinite spectrum of phenotypes or physical manifestations of sex and gender. If that wasn’t enough another compounding factor to the sex determination and differentiation schematic is that this balance changes over the course of time. It is not set in stone during embryonic development and then just continues that trajectory until death. There are changes to this balance from both internal and external factors; certain dietary or environmental factors have been labeled as “hormone disruptors” that can cause changes to how hormones operate even when the genetics is “normal.”
As pointed out in the 2009 article “A Question of Gender” Ludbrook identifies three components to physical sex development: chromosomal sex determination, gonadal sex, and anatomical sex that “for a typical woman or man all of these features are in concordance….for intersex people, chromosomal, gonadal or atomic sex is discordant.”
All of that doesn’t necessarily solve the problem of how to re-write questions like “a man with brown hair and a woman with blonde hair have kids, what’s the probability of having a kid with brown hair?” Or things like “a woman who is heterozygous for hemophilia has children with a normal man, what is the probability that one of their children will have hemophilia?” By using words like “man” or “woman” and “boy” or “girl” we are continuing to perpetuate the fallacy that sex and gender fall into binary categories where the science, even with questions still to be answered, clearly point to that is not the case.
While this is an ongoing process I have decided to add “chromosomal” in front of any sex identifier I give when discussing genetics problems. I am also going to change terminology to just indicate the gametes (egg and sperm in humans) that fuse to create a zygote instead of using “man” or “woman” and “mom” or “dad”. My hope in just using the names of the haploid cells will also be more inclusive of students who may not have relationships with biological parents or may be products of other reproductive strategies where their biological lineage may not be the same as their familial unit. My goal is to help affirm both student identities and relationships while also showing that sex, gender, and gender identity are a lot more nuanced than the chromosomal composition of any one cell (which, by the way different cells in the same organism can have different chromosomal makeups…who knew?! But we’ll save that discussion for another day).
Ainsworth, Claire. “Sex Redefined.” Nature, vol. 518, no. 7539, Feb. 2015, p. 288. EBSCOhost, doi:10.1038/518288a.
LUDBROOK, LOUISA. “A Question of Gender.” Australasian Science, vol. 30, no. 10, Nov. 2009, p. 21. EBSCOhost, search.ebscohost.com/login.aspx?direct=true&db=sch&AN=44726541&site=scirc-live.
“Human Genome Project Information Archive1990–2003.” Chromosome 1: Human Genome Landmarks Poster, web.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/chromo01.shtml.
“Human Genome Project Information Archive1990–2003.” Chromosome 17: Human Genome Landmarks Poster, web.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/chromo17.shtml.
Sekido, Ryohei, and Robin Lovell-Badge. “Sex Determination Involves Synergistic Action of SRY and SF1 on a Specific Sox9 Enhancer.” Nature, vol. 453, no. 7197, June 2008, p. 930. EBSCOhost, doi:10.1038/nature06944.
Trevor Project, The. Guide to Being an Ally to Transgender and Nonbinary Youth.