Vertegenwoordigers van OII Europe en ILGA-Europe op bezoek bij de Raad van Europa.

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Do chromosomes determine your sex?

The short answer is no. But it remains difficult for many people to understand. What was it again about chromosomes? And how can we better define sex in school and university teaching materials? This article not only explains the complexities of the diverse spectrum that is biological sex, but also addresses the problematic definition of ‘man’ and ‘woman’. It concludes that society as a whole needs to think differently about sex and gender and acknowledge that sex is not binary but a spectrum with infinite unique combinations, including what people consider ‘man’ and ‘woman’.

Three important requirements?

When ‘sex chromosomes’ were discovered and it was assumed that ‘all’ women have XX chromosomes and ‘all’ men have XY chromosomes, it was quickly concluded that the Y chromosome is responsible for masculinization. A little too quickly, actually. Later it was discovered that the SRY gene plays a role. SRY stands for Sex determining Region of Y. This is a very small piece of the Y chromosome – about 1/65,000th of the complete Y chromosome. So it’s the Y chromosome after all that is responsible for determining the sex? No, this is not true either. It was then discovered that a whole bunch of other genes also play a role. Some of those genes are part of the X chromosome, but there are also genes on the 22 other chromosome pairs that can influence the development of a person’s sex characteristics.

Schematisch overzicht voor de omzetting van cholesterol naar andere hormonen.

Schematic overview for the conversion of cholesterol to other hormones.

1 A gene’s function may be different than expected if a number of base pairs (the AT and CG combinations that make up a DNA strand) are missing, unexpectedly contain different information, or are actually duplicated.

2 But even if all these genes are laid out exactly by the book, they only function if the right hormones are made. The relationship between genes and hormones is like that between locks and keys: you need the right lock and the right key to make a gene ‘work’.
Although testosterone and estrogen are still commonly called ‘the male hormone’ and ‘the female hormone’ respectively by many people, the reality is far more complicated. This is already evident from the fact that both men and women produce both hormones, albeit in different proportions. These hormones are made from cholesterol via a set of intermediate steps using proteins. If one of the required proteins is missing, the process is interrupted: a hormone is not made, or a lesser amount is made, and the gene that is dependent on that hormone won’t work as expected either.

Buste van Aristoteles. Marmer, Romeinse kopie naar een Grieks origineel van brons door Lysippos uit 330 voor onze jaartelling. De mantel van albast is een moderne toevoeging. Foto: Jastrow 2006.

Bust of Aristotle. Marble, Roman copy after a Greek original of bronze by Lysippos from 330 BC. The mantle of alabaster is a modern addition. Photo: Jastrow 2006.

3 In addition to genes that are put together differently than expected and hormones that are not or insufficiently produced, it can also happen that a chromosome disappears completely or that an extra chromosome is added. When we’re speaking of examples of this for specific forms of sex diversity, the medical diagnoses Turner syndrome and Klinefelter syndrome show this. With Turner an X or a Y chromosome literally disappears shortly after fertilization, and with Klinefelter each cell has two or more X chromosomes in addition to a Y chromosome.

Who claims ‘XX = female, XY = male’, thus assumes three prerequisites:

  1. A good number of genes must all be laid out by the book.
  2. Androgens (‘male hormones’) and estrogens (‘female hormones’) must be present in the right amount, the right proportion and often at the right time.
  3. Exactly two sex chromosomes must be present.

In one out of 90 people this is not the case. In most cases, they don’t notice much of this themselves, nor are affected by it.

Paginaversiering: een gestileerde dubbele helix.

Intersex or DSD

When one of those conditions is not met, social scientists, lawyers, and politicians usually call it intersex while health professionals and medical researchers usually refer to it as DSD. The people affected may have characteristics of both sexes, or there may be a characteristic missing that is seen as defining a sex.

Yet it is also not the case that intersex people are ‘a little bit male and a little bit female’, or ‘in-between’ the sexes. Intersex people can tell you, just like anyone else can and does, whether they feel female, male, non-binary, or something else. Many intersex people, just like many people in general, experience their gender as either male or female. But there are of course also intersex people who identify as non-binary.

Paginaversiering: een gestileerde dubbele helix.


But what if the gender you are raised in does not correspond to how you feel? Gender is about how you feel, for example, like a woman, man, or non-binary, or anything else. There is a difference between gender identity (how you feel) and gender expression (how you present yourself to others).

American scientist Milton Diamond explains the difference between gender and sex as follows: ‘The term sex is related to anatomical structure and the term gender is related to an imposed or assumed social and psychological state. Explaining the difference to anxious parents and confused doctors takes up much of my time’ (Diamond 2002).

Sex has to do with your body and gender is based on your own experience, how you feel, see and/or present yourself. Although Milton Diamond’s explanation is clear, the words ‘man’ and ‘woman’ are used for both sex and gender and this causes confusion in practice.

Through the cracks

It is possible for the gender identity of an intersex child not to match with the assigned biological sex (and gender). This happens more often with intersex children than with kids who aren’t intersex. Recent research shows that the sex registration of five percent of intersex people has changed, mostly before puberty (Falhammar 2018). This is because it is impossible for anyone, so even for specialists, to predict future gender identities with 100% certainty. Health professionals often confuse the rejection of the assigned sex and gender with gender dysphoria, but in reality the problem lies with assigning the incorrect sex (or assigning a sex – without involving the person in question – at all). Most intersex organizations advise parents and medical professionals to register an intersex child as male or female, because it is easy to change it to male, female, non-binary, etc. (Malta 2013).

Intersex people who have rejected their originally assigned sex sometimes fall through the cracks: both transgender and DSD patient groups are often unable to accommodate them as their story differs at least in part with each group.

Paginaversiering: een gestileerde dubbele helix.

Sexual orientation

Intersex people can have any sexual orientation. However, for some it can be difficult to relate to commonly used terms.

The definitions of ‘man’ and ‘woman’ often become very important when talking about sexual orientation (in the sense of loving, or being attracted to, men, women, or those outside those two categories). People who use words like straight, gay, lesbian and bi+ assume that they know what the words ‘man’ and ‘woman’ mean, and it is practical for them to use simple definitions. After all, when you meet a potential partner, you don’t want to start discussing at length what your definition of man and woman is. But this simplicity is an obstacle for those who do care about a better definition. For example, intersex people can bud heads with people who use these terms in a way that is not inclusive.

But it may also be that the definition of male and female is not so important at all. You could even say that those who accept the many nuances of both sex and gender can no longer distinguish between straight, gay, lesbian and bi+. After all, what does ‘people of the same sex’ actually mean if you accept that everyone’s sex and gender is different and unique?

Paginaversiering: een gestileerde dubbele helix.

School books

It is a common wish of intersex people to adapt the information taught in school. The simplest solution only requires the addition of the word ‘usually’ when talking about chromosomes: XX is usually a woman and XY is usually a man.

But this does injustice to people with a chromosomal variation, described in medical terms for example as Turner Syndrome, Triple X Syndrome, and Klinefelter Syndrome; they are thus implicitly still seen as abnormal. Moreover, there is a good chance that other characteristics will then be seen as determining gender: a woman is someone who can bear a child. Or a woman is someone with breasts and a vagina.

The latter would not do justice to many intersex people, but it would also not do justice to gender-diverse people. Women who have had their uterus or ovaries removed are also excluded by a definition of man and woman that is based on reproductive organs. Research shows that this danger is not imaginary: women who had their uterus and/or ovaries removed create a social construct in which they begin to measure their femininity by the extent to which, after the surgery, they still conform to the norm that a woman has two ovaries (Jean 2003).

A good solution will require society to think differently about sex and gender. That will take more time and effort than simply adding the word “mostly” to school textbooks and scientific publications. But replacing an oversimplified view with another oversimplified view is not a solution. In order to reach a good solution, however, organizations that focus on sex diversity should collaborate with other organizations who deal with gender and sex constructions, for example (but not limited to) transgender or LGB organizations.

Paginaversiering: een gestileerde dubbele helix.