Beyond X & Y

Beyond X & Y: Chromosomes and Sex Organs

When it comes to sex chromosomes, there's more to it than XX or XY

October 26, 2020
The letters "se" and "xy" moving toward each other horizontally, pressing together, and then separating as "s" and "x" move upward and "e" and "y" move downward out of frame
Gender and sex beyond X & Y. [Credit: Niko McCarty | CC BY-NC-ND 2.0]

Welcome to Beyond X & Y! This blog will explore all things gender and sex, and there’s a ton of ground to cover. Just a few of the topics I aim to explore include the latest studies on sexual and reproductive health, psychology and gender, sex worker health policies and more — including the titillating stuff.

Let’s start with the bread and butter: genes.

Sex and gender are complex, and our understanding of both is constantly evolving. Even a quality as seemingly simple and binary as biological sex is a spectrum rather than an either/or. In fact, sex chromosomes — and how those chromosomes translate into physical features — can vary in quite a few ways.

Here’s what’s regarded as the “norm”:

XY chromosomes = penis & testes = man

XX chromosomes = vagina & ovaries = woman

Gender is subjective to each person, and sex organs don’t dictate gender. People with penises aren’t necessarily men, and people with vaginas aren’t necessarily women. The thing is, XX and XY chromosomes aren’t cut and dry, either. Actually, sex chromosomes and genetic expression vary widely, beyond a penis/vagina or XY/XX binary. XX and XY with the aforementioned expressions are the most common sex chromosomes and corresponding organs, but they’re not the only ones.

Some people have differing sex chromosomes, such as those who are born with an extra X chromosome (XXY) or who are missing an X chromosome (XO). Or, some people with XX or XY chromosomes might have physical characteristics that don’t seem to align with what’s typically expected of their DNA. All of this is to say that many bodies that exist outside of the assumptions that come with XX and XY sex chromosomes.

One word that often describes these bodies is “intersex.” Intersex is an umbrella term that describes any person whose sex characteristics do not neatly fit into binary categories. Intersex people might have sex organs that include both XX and XY sex characteristics. Babies born intersex are often subjected to superfluous surgery in infancy in order to make their genitals appear either male or female.

Being intersex itself is a spectrum. It’s not always clear-cut when someone is intersex. What’s considered an abnormal size for genitalia? What about when someone has sex organs that align with one binary, but secondary sex traits that do not? Like gender and sexuality, genetic expression varies, too. There is not just one way to be intersex. Here are just a few examples of intersex variations:

Klinefelter Syndrome (XXY chromosome)

A person with this condition has an extra X chromosome, and is usually socialized as male, meaning the doctor will say, “It’s a boy!” at the delivery, and the baby henceforth will be treated like a boy. Affecting about 1 in 650 newborn boys, this is one of the most common sex chromosome variations.

Turner Syndrome (XO chromosome)

While a functioning pair of X chromosomes is common, some people only have one functioning X. They are usually socialized as females (“It’s a girl!”), and have underdeveloped female sex characteristics.

Swyer Syndrome (XY gonadal dysgenesis)

A person with Swyer Syndrome doesn’t have functional sex glands, and typically appears female. The glands they do have are known as gonadal streaks — slightly developed gonad tissue. Those with Swyer Syndrome will not develop secondary sex characteristics (e.g., breasts, Adam’s apple) without hormone replacement because gonadal streaks cannot produce sex hormones characteristic of puberty.

Congenital Adrenal Hyperplasia (CAH)

CAH is the most common cause of intersex traits in those with XX chromosomes. It does not cause intersex traits in those with XY chromosomes. CAH results in an imbalanced production of hormones from adrenal glands, which are hormone-producing glands above the kidneys. The glands create an unusually high amount of virilizing hormones that can result in physical characteristics such as a deep voice, dense body hair and prominent musculature.


These sex glands include both ovarian and testicular tissue. One with this condition can be born with any combination of ovaries and ovotestes. The genitals of a person with ovotestes may appear more typically male, female or somewhere in between.


Some might argue that the fact these physical traits are called “syndromes” or “conditions” means there’s something wrong with the individuals; they have an illness or irregularity. Just because someone is different doesn’t mean there’s something wrong with them. Equating the two results in the stigma that often comes with being intersex. 

Others might argue that intersex people might be sterile, which definitely indicates that something’s wrong or “not natural.” Equating fertility and humanity harms everyone, not just intersex people — plenty of cis men and women are sterile, but each one is no less of a person. Reducing a person to their reproductive organs, and even to their genes, and only rendering two viable options fails to recognize a swath of the population, harming our concept of human sexuality, and — sometimes literally — the people it tries to erase.



About the Author

Elana Spivack

Elana Spivack is a science writer in New York City. When not on deadline, she enjoys salsa dancing, bike riding and befriending bodega cats.



Pierce scranton MD says:

What an intelligent discussion. Not judgmental. I like the conclusion:being different does not mean something’s wrong. It might be easy to go on and on, but this discussion should strip away some of the emotional knee jerk attitudes.

Wanderer says:

Here is a radical thought. Having something wrong does not make you less of a person. I have cancer, if i don’t acknowledge that, then I am stupid. I can feel anything I want, but facts need to be addressed or I need to make peace with it. Either way, no one says ‘oh you are less of a person’.
Similarly – if you have a genetic defect in the code (in your DNA), that is outside your control. It could have come from having a drug user, smoker or drinker for a parent and that is outside your control. That is their fault. Or it could be pure bad luck. Leave it, make peace and see how to become a productive member of society.
Seek help if needed, never shy away from that. You are an individual, who has something to offer. Live your life to the fullest.
BUT FOR THE LOVE OF EVERYTHING IN THIS UNIVERSE, DO NOT misinterpret facts or change definitions to suit your needs. That does tremendous harm. Never hide from things.

XX says:

The fact that you have a disorder and have an extra x chromosome or are lacking one is the same as someone born without a limb or an extra one. It does not mean it is to be viewed as normal when in fact it is abnormal. This is not science it is MK ultra mind control. XX is Female and XY is male. Genetic abnormalities do not make the genders obsolete.

Mike Bobby says:

People may think this isn’t normal or something is “wrong” with you, but this sort of thing is naturally occurring and had been normalized in many cultures for a VERY long time. We didn’t understand it as well as we do today and colonization’s destructive touch to the cultures that they encroached upon caused major setbacks. Society as we know it has literally gone backwards and covered its eyes rather than accept the science we can see ourselves now. Thanks for this, though, it’s nice and easy to comprehend. It’ll be useful to hand to people who want to know more without overwhelming them.

truth teller says:

No data. questionnable sources. and frankly, very little common sense. why do we teach that humans have 10 fingers? because it’s the norm. Maybe you should keep doing salsa dancing because you really aren’t that bright…

Rose villareal says:

Not only questionable sources but biased as well.

Michael says:

Very nice, simple article. Good starting point for further reading on the subject. Well done and thank you.

Erik says:

Hmm…if people have a nose with two nostrils and they identify single nostril will we have to accept their dilution?

Michael Devereaux says:

When an XX person can identify as male, and an XY person can identify as female, then we have moved away from science into some type of bizarre belief system that has nothing to do with science nor the human species.

Teri says:

The many many vaccines I believe play a huge factor..when you mess with God’s creation well it’s not good let me just say that.

19 And of every living thing of all flesh, two of every sort shalt thou bring into the ark, to keep them alive with thee; they shall be male and female.

Matthew Elliott Rand says:

What was the recent scientific discovery that occurred which revolutionized the way we talk about the human species?

I learned about Klinfelter’s syndrome and the like back in the 80s, but it was never suggested that we should take the term “gender” out of its linguistic context to talk about the nature of the human species. In fact we learned that male refers to an organism that produces the motile gamete, and female refers to an organism that produces the sessile gamete. A man is a human male, and a woman is a human female.

I’m just wondering from a scientific perspective where this understanding was found to have been inadequate.

Gary says:

Keeping this really simple. The presence of a Y chromosome means the person is male.

Yes, even in XXY configuration ( 1 in a 1000 births), also known as Klinefelter syndrome.

Paul says:

The article makes good points, but they want to make it sound like 1 out of 4 people have one of those anomalies, when in fact it’s 1 out of thousands at times. They want to try and minimalize how the overwhelming majority of people walking the earth are XX and XY. But it does get one important point across … gender is fluid, but you CANNOT change your biological sex. The argument is “there are only two genders,” but that’s the wrong argument. There are only two sexes, but there can be different genders. Gender is social, sex is science.

DJP says:

I must agree with Paul’s comment above and some of the others. Nobody is saying someone who is intersex is less of a valid person, or that sterile people who live per their birth designation are lesser people. But does that have any relevance to the existence of biological sex. It seems to me that some are trying to make biology fit the more nuanced nature of social gender because they want it to. But it doesn’t and why does it matter ?

Every human on the planet or who has ever been on the planet has been the result of mating between two pretty clearly distinct biological sexes. Those in between or infertile are equally valid humans but don’t create new humans. So surely biological sex is a demonstrable fact.

People talk about embryos not showing male or female characteristics in early stages that suggests that it’s all up in the air and sex could go either way….. But biology does decide a sex by the time (long before) the embryo is born, it’s not decided by later decisions or social environment. Societal gender may be and that is different, but not biological sex. Difference in hormones as far as I can read up on does not always distinguish which side of the biological sex line people fall on.

Roxanne Colona says:

Good starting point for a discussion. I see comments assuming the chromosomes of individuals are “normative” and if they are something else it is BS. My question would be that most people have no idea what their chromosomes indicate. They have NEVER been tested. They just assume what those chromosomes are because the genitals they see match what they feel inside. Well, lucky you, but that is not the experience EVERYONE has. If all those people were tested, how many more would fall outside the XX XY binary? Moral of the story-not your business to judge. The individual and health professionals should take the lead.

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