#note: trisomy 13 in humans is also technically viable for life

[gay-jesus-probably]

If you know anything about chromosomes, you should know that sex chromosomes are barely relevant to a person. There's a reason it's the only form of monosomy that presents in humans - you just need one X chromosome to set up some hormone systems and whatnot, and there you go, you're viable for life. I mean, Monosomy 23 isn't great for a person, they'll probably be sterile, their bone structure turns out a bit fragile, and they'll definitely need hormone therapy to properly hit puberty, but it's a life. Which is a hell of a lot better than any other form of monosomy in humans, which comes with lethal structural flaws ensuring you don't make it to birth.

Anyways, the far more common issue with sex chromosomes in Trisomy 23, and I say 'issue' in the loosest sense of the word, because honestly it's not even a problem - we have no idea how common Trisomy 23 really is, because there's basically no symptoms, and every form of it presents about the same. As in, the first case of XXY trisomy was discovered accidentally - the man who had it was getting a karyotype test done for completely unrelated reasons, and was shocked to discover he had a trisomy.

Sex chromosomes are neat like that; since they're literally designed for everyone to have an X no matter what, the way it works is that you just need to have one X chromosome, and there you go, you've got the structural information you need, you're viable for life. The other sex chromosome (or chromosomes) is just a modifier for what configuration the reproductive organs should be in. So the Y chromosome carries very little information, since it's only relevant half the time, and the X chromosome is meant to be able to work through a redundant copy, which leads to the end result where Trisomy 23 does basically nothing. Unless you've had a karyotype test done, you have no idea what's actually going on with your sex chromosomes, and neither does anyone else.

Like... come on people, they're so meaningless. Chromosome pairs are numbered from most to least important, you know; there's a reason the sex chromosomes are all the way at the end, and that's because they're barely relevant. Humans just don't have a lot of sexual dimorphism; we're a very androgynous species.

And all that stuff about Trisomy 23 stands in very sharp contrast to the other survivable forms of trisomy in humans, which is... arguably one and a half kinds. Trisomy 21 (aka Downs Syndrome) is the best known, as it's the only other form that's really viable, since it fortunately just presents as some mild structural issues - the brain's a little scrambled, and the heart has some fundamental flaws that cut about twenty years off the average lifespan. For a trisomy patient, that's incredible. If you've got Downs, you technically lost the genetic lottery, given that you had the bad luck to get either a sperm or ova cell that'd suffered a nondisjunction during the meiosis process, but I'd argue you also won the genetic lottery, because my god your existence is a miracle, we're so lucky that the 21st chromosome pair just happens to not cover anything too vital. And you're absurdly lucky that the defective sex cell that started it all just so happened to have that specific form of nondisjunction, because if any chromosome pair apart from 21 or 23 is affected by nondisjunction during meiosis, it's extremely not good.

...Then there's also Trisomy 18, which is... hard to describe. I mean, it's amazing that Trisomy 18 cases can survive until birth, but... the structural flaws are considerably more severe, so most don't last long after that. Most Trisomy 18 patients die within a week of being born. The lucky ones get a few months or years. With constant, intensive medical care and a hell of a lot of luck, a tiny handful of patients have even survived to their twentieth birthdays... but never for long after that. There's a reason why treatments for Trisomy 18 include grief counciling for the parents. It's just... it's not good. There's a reason I said Trisomy 21 is a miracle; other forms of trisomy in humans are so, so much worse.

Except for Trisomy 23, which again, barely counts, because there are no symptoms, and so we have no idea how common it really is. Are you slightly taller than average? Congratulations, you might have Trisomy 23. Or you might not, who the fuck knows. Certainly not you!

Basically my point is, chromosomes are absolutely fascinating, but the sex chromosomes are only really interesting in the context of how irrelevant they are compared to all the other chromosome pairs. They're just not doing all that much, so there's a massive amount of room for error with no real signs. All anyone knows for sure is that they have at least one X chromosome (as that's where the important information is; no X means no life), and beyond that if you haven't had a karyotype test done, it's just wild guessing. So if you're ranting about sex chromosomes being A Big Deal... congratulations, you've exposed yourself as a fucking moron that knows nothing about chromosomes. Anyone that's studied biology beyond a high school level could tell you otherwise. Rip to all you bioessentialists but I'm cooler than you.

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[oojamaflip-whatchamacallit]

#note: trisomy 13 in humans is also technically viable for life#but thats a strong technicality so i didnt bring it up#yknow how trisomy 18 patients rarely live past toddlerhood? trisomy 13 patients never do.#too depressing. didnt want to talk about it.#...dont look up photos of trisomy 18 or 13 btw#wasnt joking about it coming with massive structural errors#its... a lot of photos of babies that dont really have faces. and probably didnt live long after those photos were taken#i mean do look it up if you're interested. but just be warned it's all pretty grim stuff#anyways science is awesome and cell division is fascinating to me#trisomy/monosomy occurs when meiosis goes wrong. the chromosome pairs are torn in half in the process#sometimes they dont make a clean split. then you have one sex cell with monosomy and one with trisomy!#meanwhile if mitosis goes wrong if you're lucky apoptosis occurs the cell dies and nothing happens#if the defective cell doesn't undergo apoptosis congratulations it's a cancer cell. good luck with that#alright infodump over back to your regular scheduled shitposting

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