#chromosomes

[mindblowingscience]

The sex of human and other mammal babies is decided by a male-determining gene on the Y chromosome. But the human Y chromosome is degenerating and may disappear in a few million years, leading to our extinction unless we evolve a new sex gene. The good news is two branches of rodents have already lost their Y chromosome and have lived to tell the tale. A 2022 paper in Proceedings of the National Academy of Science shows how the spiny rat has evolved a new male-determining gene.

Continue Reading.

[queerism1969]

I'm not saying @jk_rowling is a male. I'm just saying we have zero proof that she's not a male. And until we see her chromosomes, can she be trusted in women's spaces?

[dhddmods]

Intersex Guide!

Hello and happy pride! We wished to share a passion project we have been working on for months - a guide to intersex traits and variations! Please reblog to spread awareness.

Now, a question that many ask - what is intersex? Well, we will be answering that question for you here! Anything on this post that is written in red is NOT intersex, so if you wish to skip over any of it, you can. And if you wish to get straight into the intersex types, scroll down to the read-more and start from there.

Intersex, also known as the intersex spectrum, is a term used to describe when someone's biological sex - as in the sex they are born with/what they naturally develop during puberty - is not clearly defined as the typical male or female sex traits.

(This does not include someone that was born male or female, and later chose to have their sex traits changed due to being transgender, transsex, or altersex. It also does not include males that experienced circumcision/dorsal slits or penis splitting, females that experienced genital mutilation, or males & females that indulged in modifications such as piercings and beading.)

This only applies to primary sex traits - chromosomes, genitals, reproductive organs, and hormones. Atypical secondary sex traits (breasts, muscle tone, body/facial hair, deepness of voice) do not make someone intersex unless it is paired with "abnormalities" in primary sex traits.

Before you can understand what it means to be intersex, first we must clarify what it means to not be intersex.

A typical male has XY chromosomes, a penis, two testicles within the scrotum, and more androgens (mostly testosterone) than females. Upon puberty, they usually (but not always) develop more facial hair & muscle tone than females, and a deeper voice than females.

(Note: A penis has a phallus, a scrotum beneath the phallus, foreskin protecting the head of the phallus, and a urethra on the head of the penis. It is is straight or slightly curved when erect.)

A typical female has XX chromosomes, a vulva, two ovaries, a single uterus, and more estrogen than males. Upon puberty, they usually (but not always) develop larger breasts and wider hips than males.

(Note: A vulva has two labia, a single pea-sized clitoris, a single vaginal entry, and a urethra above the vaginal entry and under the clitoris.)

Here is a list of non-typical sex traits that, by themselves, are not intersex.

Accessory Breasts (Polymastia): Having more than two breasts. Accessory Nipples (Polythelia): Having more than two nipples. Athelia: Having only one nipple, or no nipples at all. Amastia: Having only one breast & nipple, or no breasts & nipples at all. Breast Hypertrophy/Macromastia/Gigantomastia: Having extremely large breasts Gynecomostia: Breasts on a male. The reason this is not considered intersex is because all sexes (except for people with amastia) have breast tissue, which can vary in size regardless of sex. Females can have small breasts, and males can have larger breasts than is expected. Hypotonia: Low muscle tone. Bicornuate Uterus: A heart-shaped uterus. Septate Uterus: A uterus that internally has a partition down the middle. Macropenis: A penis that is 7 inches/17.78 centimeters or larger. Macroorchidism: Testicles that are 4 milliliters or above pre-puberty, and above 30 milliliters as an adult. Macrovagina: A vagina that is deeper than 5 inches/13 centimeters. Labial Hypertrophy: Labia that is longer than average (above 2 inches/5 centimeters)

Now, onto the intersex spectrum! First, some notes.

-An intersex trait is a singular atypical trait. For example, someone with ambiguous genitals, but no other "abnormality" has an intersex trait. -An intersex variation is when multiple atypical traits are present, with at least one of them being an intersex trait. For example, someone with ambiguous genitals and fused kidneys has an intersex variation. Equally, someone with ambiguous genitals and cryptorchidism also has an intersex variation. -CTF stands for "close to female." CTF traits are when the traits are predominantly "feminine" (vulvas, uteruses, ovaries, estrogen as the main sex hormone, breasts, widened hips, XX chromosomes, etc.) -CTM stands for "close to male." CTM traits are when the traits are predominantly "masculine" (a penis, testicles, androgens as the main sex hormones, increased hair growth, higher muscle mass, a deepened voice, XY chromosomes, etc.)

Also, when we state that an intersex trait/variation is "fairly common", we mean that it is fairly common amongst the intersex population, not that it is fairly common in the general population. Being intersex is still classified as "rare" statistically speaking (as statistics define "rare" as 1 in 1,000 people.)

So for the sake of this post, here is how we are classifying the following:

"Fairly common" = 1 in every 5,000 (or less)

"Rare" = above 1 in every 5,000, up to 1 in every 100,000

"Extremely rare" = above 1 in every 100,000

Similarly, when we say "higher risk of _", it does not necessarily mean that risk is very high, just that its a higher chance than a person without that trait/variation. It could be as low as 1% higher of a risk. Every sex has its risks, whether its male, female, or on the intersex spectrum. To put it into perspective, females are at a higher risk of breast cancer than males.

Also, keep in mind that "may include" means that not all of the features will be present on every single person with that variation; in fact, none of the extra features could be present. However, for chromosomal variations specifically, it is highly likely that at least 1-5 (or more) of the listed extra features will be present.

And finally, when we say that "fertility is average", what we mean is that the gonads are fully capable of producing healthy average numbers of sperm/eggs, and/or the uterus is capable of carrying healthy babies. Struggles with the sperm reaching the eggs still might occur, but if direct insemination is done (as in the sperm is directly injected), then pregnancy should occur perfectly fine.

---

Penile Traits/Variations (not including those on the agenital spectrum)

Urethral Traits/Variations (not including those on the agenital spectrum)

Ambiguous Genitals

The Agenital Spectrum/Agenital/Agenitalia

An umbrella term, describing those born with no genitals, closed-off genitals, small genitals, or genitals that are missing typical penile or vulval traits.

(Anorchia & Monoorchidism fall under this as well.)

Gonadal Agenesis

An umbrella term, describing an individual that is born with an absence of one or both gonads (ovaries, testicles, or ovotestes).

Other reproductive traits/variations

Hypergonadism

An umbrella term, describing an individual that is born with gonads that produce high levels of hormones compared to males and females.

Hypogonadism

Primary Hypogonadism/Hypergonadotropic Hypogonadism: when its the gonads themselves that have low production levels. The brain is still communicating to produce the average male/female levels of hormones, but the gonads are failing to keep up with the brains-signals.

Secondary Hypogonadism/Hypogonadtropic Hypogonadism/ Central Hypogonadism: when the brain has low levels of communication with the gonads. The brain is failing to send out typical levels of signals to the gonads, and the gonads only produce hormones when a signal is received.

Other Hormonal Variations

Chromosomal Variations

And thats all!

Again, please reblog to spread awareness. Intersex people are highly discriminated against. Their bodies are still regularly mutilated at birth, in order to make them "look right."

This mutilation can cause complete infertility, a loss of sensation in genital areas (making sex unsatisfactory), gender dysphoria, body dysmorphia, and even chronic pain.

Additionally, intersex children are often bullied at school for looking or sounding "abnormal" for their age/gender. And as they grow up, they face the same difficulties transgender individuals do - judgement for not being a "real man" or "real woman" (or for being non-binary), difficulty dating, struggles finding jobs, complications in receiving proper healthcare, and they are at an increased risk of being abused and assaulted. Many are also left out of sports or kicked out of public bathrooms as well.

This is all due to the lack of education. Tolerance and acceptance needs to be taught to children. Many doctors have no idea how to treat intersex patients, as they didn't learn about their bodies, even in advanced schooling. We need to put a stop to this.

[crossdreamers]

A guide to chromosomal variations

Over at Instagram Melly the Science Geek has published a mind blowing video about how chromosome decide (or do not the decide) the sex of a person.

The world is a a very complicated place, indeed.

And at this point we have not even begun to talk about gender identity.

The Science Vet on XX, XY and all the other variations

Melly's video reminds us of the very popular twitter thread made by the Science Vet back in 2018.

We take the liberty of republishing that thread here:

So. Hi new people! Apparently, we're gonna talk about sex. Like physical sex! Because... there's some confusion.

First, sex defined: We're talking physical sex here, not gender. Body parts, hormones, and genetics (and more).

BLUF: BIOLOGICAL sex is a spectrum

Ok, everyone's super familiar with the XX/XY dichotomy, right? Yeah, what we all learned in like... 4th grade? And that's great, it gives you a starting point. But it's... well it's only the very starting point.

The IDEA is, XX is girl, XY is boy, right?

Welllll... that's not totally right. There are XY people, who have ovaries! And give birth! AH! And XX people who have male bodies and functional sperm! Double AH!

These are usually written off as "abnormalities" and indeed, some cases have medical issues. But many don't (like the XY woman giving birth). And this is really only the very very tip of the iceberg of "wait, that doesn't fit into our M or F box unless we make it bigger"

There's a WHOLE HOST of things that can cause all sorts of "weird" things to happen, ranging from genetic (XXY, XYY, Y, X, XX with translocation, XY with deletion) to hormonal (Androgen Insensitivity, Estradiol failure), and disruptors like dioxins

So, you're a scientist, and you want to research stuff, right? Which means you have to categorize stuff. Without categories, data is hard! So you take allll these people, including the "weird" ones and you plot them on a graph. Logical!

You use all the differences there are, different genetics, different responses to hormones, different effectiveness in signalling pathways, different sizes in Aanteroventral periventricular nucleus (AVPV) (yeah that's a thing) and give everything numbers, add them up.

You get what's called a bimodal distribution (mostly, we'll get to that later) Which looks like this. Those two big peaks are what we call "male" and "female" (even conveniently colored pink for boys and blue for girls - we are using victorian gender colors right?)

/8

Now, when you're trying to look at data, we often group stuff. When we do that with a plot like this, it's called a "histogram." Basically we're breaking down a curved line into discrete "bins." Like this (image stolen from the web).

/9

Traditionally, we've used REALLY BIG bins for this when talking about sex. Basically you either group everything vaguely near a peak into the peak, or you just pretend there's nothing else but the biggest peaks. This makes it super easy, because 2 is simple to do data with.

However, as we've gotten to know more and more about signaling and brains and hormones and started to pay more attention to the outliers where standard stuff just didn't seem to work, we discovered that this isn't a great model to use.

Now I'm not talking feelings here. I'm talking about data. As you start to look at anything interesting, like say the effects of 2,3,7,8-Tetrachlorodibenzo-P-dioxin on animals, you start to realize that a 2 bin model doesn't predict your results well.

At first you say, "Well it was just weird." So you redo it, and it still doesn't work. So you look at your model and you say, "Well ok, what if the model's wrong?"

But the model sort of... almost predicts a lot of things, and it worked for years, so...

Some enterprising soul says, "Hey, remember that histogram where we said we'll just model using the peaks?" And everyone goes, "Uh, yeah?" And they say, "What if we... USED that data?" And everyone groans, because complicated data is hard.

But someone sits down and does the work, and lo, wow the model starts to work again. Where TCDD was "randomly" turning some boys into girls but then some girls into boys, now you can see there's a subgroup of what you'd called "female" that responds like the "male"

What's important here is that you haven't MISLABELED males as females. These are functional "females" who can do all the usual "female" things like gestate babies. But they respond to this one endocrine disruptor in a "male" way.

So you add another two categories, call them "Male2" and "Female2" and go on, happy that your model works! You've got 4 sexes now, but you don't really have to tell anyone that, right?

Exceeeept then you remember you've got those XY people that gestate babies. So you add "Intersex1" And then the XX people with penes... and ovaries? Ok, "Intersex2" because all these groups respond differently with signalling and brains when you get into the weeds

And the more you look, the more we LEARN, the more we're able to separate out those fine differences. Depending on what we're doing, we may not care. If a doc is giving you aspirin, it probably isn't a big deal.

But if they're using a steroid on you? Or treating dioxin poisoning? THAT SHIT COULD BE IMPORTANT. It's like saying, "the light's off so the power must not be flowing." It really matters if the light's off because the bulb blew.

If we go back to that histogram plot, we can keep breaking down your biological sex into smaller and smaller differences in brain areas, hormone levels, signalling differences, genetic variances. There's nothing stopping us from binning EVERY INDIVIDUAL into their own bin.

Technically, this wouldn't be "infinite sexes" but 7.4 billion sexes is functionally close for our brains. Now, our medicine isn't advanced enough for THAT level of detail to make any difference. BUT IT MIGHT BE in the future. Individualized medicine!

The thing to remember is that this isn't "new." We're not 'inventing sexes' here. Sex has ALWAYS been this curve. We were just using REALLY BIG bins. And now we're realizing that that's not representative of biology, it's inhibiting understanding of medicine and biology

In case anyone's curious, this isn't ideology. This is because I had to figure out why my data didn't match the prediction. Those rats I mentioned? Yeah, my lab. And lab rats are a really pure genetic monoculture, and they STILL don't fit the two peak model well.

So, since it's come up, an addendum!

Yes, we looked at other things we could do to make our data fit the existing model, that's how science works! The ONLY way the data fit was if we let "sex" be more than just those two narrow peaks.

Models purpose in science is to predict. If they don't predict correctly, first we check if we've measured the data correctly, and repeat the experiment a couple more times. If it still doesn't fit, we have to look at the model.

Intersex! Because I didn't specifically mention this.

"Intersex" is a grouping bin used for a lot of the "middle ground" of the spectrum between the "male" and "female" peaks. Any situation where easily assigning the person to one of those two peaks is challenging.

Intersex! Because I didn't specifically mention this above.

"Intersex" is a term used to collectively speak of the "middle ground" of biology where people can't easily be binned into those two big "male" and "female" peaks. It can include a large range of biology

It is worth noting that I never talk about transgender in this thread. Intersex is not the same as transgender. You can be one without the other, or be both.

For people who think this is just "outliers"

Current estimates are that the intersex population is at least 2%. We know that's low because there are a lot of "invisibly intersex" people. That means AT LEAST 150 million people in the world.

I apologize for the failure to use the word "intersex" higher up in the discussion. Many people in the middle ground (including the XY person who can carry a child, for example) use this term. I cannot go back and edit the thread, and apologize for my overly clinical description. 

Part of the purpose of the thread, which may have failed, was to point out that "intersex" is not a condition, it is not a disease. It's natural with a bimodal distribution. Science not only supports this, it suggests that ignoring intersex people makes your conclusions wrong 

References at the end of this page.

[biologist4ever]

Cell Division: Stages of Mitosis

[hjellacott]

Interesting stuff about XX chromosomes I found out today after speaking to a Geneticist

So for health reasons yesterday I had a long conversation with a geneticist from the NHS, regarding hereditary health conditions, that I found so interesting I thought I'd share some of it with you.

She explained that for example, when it comes to say, physical disabilities caused by genetic problems, we have two genes in one X that are related to that, and one, in plain language, has "misspelling", causing the issue. But you still have the other gene that sort of compensates, in some cases. So males, they only have XY chromosomes, the X inherited from the mother, and the Y from the father. Therefore in males, they would only have two of these genes. But not women!

Women's biology can be absolutely extraordinary. We have XX. Two X, one from our mother and one from our father, so whatever faults one X gets, very often the other X can act like a backup copy. So for example 1 X gets say Gene Ding (I made this name up) damaged, causing mobility problems. But then 2 X has a totally healthy Gene Ding, therefore it compensates, and the symptoms become much better, and even inexistent in some cases.

That's why in some cases, with some genetic issues, women experience less symptoms than men! Isn't that totally incredible? Here I was thinking women got the worst end of biology with the period, but turns out we're not doing that bad!

[geminisee]

via mirrorhopper (captions added by me)

[deebrisbyfish]

Soooo, I generally DON'T get political or divisive in the strip... buuuuttt... it's PRIDE and, like with last week’s strip, I am kinda burnt out with seeing the same asinine arguments online over and over. Why do I have to defend my legal right to exist with people who learned biology from "Kindergarten Cop"?

[economicsresearch]

pages 225 and 226 - has my life been productive?

No kids that I know of. No party I could say no to. Working just enough (see previous answer). Minimal responsibility for destruction of the rain forest (had a bit of a passion for açaí berries in the mid oughts I will admit). Tried to feel good. Tried to make others feel good.

But I don't remember starting any factories, so I guess the answer is no.

But I don't get it MAN.

This person is called screaming debbie by the way, because those orbs come screaming at you when you're playing the game orbs.

[bpod-bpod]

Counting X’s

A study in fruit flies provides greater understanding of the mechanisms regulating sex determination (according to the number of X chromosomes) in the germline (that ultimately forms eggs or sperm) – the role of a transcription factor called sisterless A (sisA) revealed

Read the published research article here

Image from work by Raghav Goyal, Ellen Baxter and Mark Van Doren

Department of Biology, Johns Hopkins University, Baltimore, MD, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in eLife (reviewed preprint), August 2024

You can also follow BPoD on Instagram, Twitter and Facebook

[mau-mao]

4 Ways a Male Cat Can Be Tricolor

The X chromosome in cats determine their fur color. This gene has two alleles, one for orange fur (XB) and one for black fur (Xb). Females carry two X's and males carry one X, allowing female cats to have two colors while restricting male cats to one. Therefore, it is extremely rare for calico males to exist!

Klinefelter Syndrome (XXY)

Male cats with an extra chromosome (X)

Allows for the expression of both orange and black pigments

Infertile

Extra X chromosome interferes with sperm production

Chimerism

Two embryos fuse together early in development, leading to a single individual with cells from both embryos

Allows for tricolor pattern in males

Sometimes fertile (depends on if the combination affected the reproductive organs)

Only one of their colors will be passed on to offspring

Mosaicism

Individual cat has two or more genetically different types of cells within their body

XXY cells and XY cells found in the body

Sometimes fertile

Only one of their colors will be passed on to offspring

Birthmark

Might be a patch of a different color or shade on the skin or fur

Does not result in a true tricolor pattern, but still causes variations in fur color

Fertile

Birthmark color does not affect offspring color

[clownrecess]

I want to talk about 22q11.2 deletion syndrome, because I have it and it's something I've genuinely never seen spoken about!

22q11.2 deletion syndrome is a condition where a person is missing a part of chromosome 22. Some common things caused by it include heart defects, immune system issues, developmental delays, learning disabilities, and psychiatric conditions.

Anxiety disorders, ADHD, autism, and mood disorders are commonly found in people with 22q11.2 deletion syndrome.

Not a big post because I didnt have too much to say about it, but it is something I wanted to talk about.

[biologist4ever]

Cell Division: Stages of Mitosis

[nando161mando]

Just a reminder that we used to do chromosome testing of athletes up until the mid to late 90s. We stopped because both male and female athletes kept finding out they were a different gender than they thought. And at least one elite athlete kept getting a different result every single time she tested, leading the IAAF to rule that the chromosome testing is "shown to be inconclusive in identifying maleness."

[obaewankenope]

You know... All this hatred Jk Rowling has for transfolks and her doubling-down on gender being an X or Y science thing... It would be beyond hilarious if Rowling did the chromosome test and found out she had one of those rare chromosomal variations (like Klinefelter Syndrome: XXY chromosomes, or Swyer Syndrome: females with XY chromosomes) that meant she wasn't a "real" woman by her own standards of XX only lmao

Like, I feel like that would be fitting for the woman who stirs up so much transphobia and goes on and on about male on female violence about the Olympics and then tries to double-down on it not being about the athlete directly but "obviously" it's a more general thing and how it looks and blah blah

Just... Hey Joanne. Joanne, hey. Why don't you do the DNA test and release the results and show us your chromosomes? Give us that very private information in a public sphere on the internet where nothing really dies to prove you're really a womanly woman. Hmm... No? Odd how you don't want to do that but demand someone else should.

Gods I fuckin hate her

[traditionaldream]

I'm curious what the term "woman" means to you based on your post. (I don't think that your views are wrong, or horrible. I'm just genuinely curious.)

For me, a woman is somente who has XX chromosomes. A man is someone who has XY chromosomes; this can't be changed, no matter what you do to your body. You can call yourself whatever you want, but down to your bones you are what your DNA says you are.

Of course I know not all women mestruate and have breasts due to, for example, illnesses, but if they have XX chromosomes, they are women.