Okay, sex determination in humans.
This shit is COMPLICATED and this will probably be a longish thread. Sorry. But I've seen a lot of people claim that "biology says" that everyone is either male or female, full stop, and it's just not true. 1/22
… MIS is around to stop them. So SRY can coordinate a program that shunts the default female development into male development.
Chromosomes can break and pieces can rearrange, so some people get a Y chromosome without an SRY gene, and are usually seen as female at birth. 5/22
Without some other genes on the Y chromosome, and with 2 Xs, these people do not exactly develop the "normal" male program.
But it's a LOT more complicated that that, even. 7/22
Most complex and controversial of all of this, it is *likely* the case that part of this program happens in the brain.
No one really knows what "masculinization" or "feminization" of a human brain means! (Though very smart people are earnestly trying to figure it out.) 16/22
So mutations exist that produce anatomically male flies with female behaviors, or vice versa.
People are VASTLY more complex than flies and our brains are much more flexible. It's not clear, after decades of looking, that male and female brains are genuinely different. 18/22
The development of a eutherian mammal as a male is a consequence of testis formation in the embryo, which is thought to be initiated by a gene on the Y chromosome. In the absence of this gene, ovaries are formed and female characteristics develop. Sex determination therefore hinges on the action of …
@stevegis_ssg biology is weird and squishy. There is also the strange case of chimerism, women who are the biological aunts and not mothers of their own children:
https://embryo.asu.edu/pages/case-lydia-fairchild-and-her-chimerism-2002
In 2002, after applying for government assistance in the state of Washington, Lydia Fairchild was told that her two children were not a genetic match with her and that therefore, biologically, she could not be their mother. Researchers later determined that the genetic mismatch was due to chimerism, a condition in which two genetically distinct cell lines are present in one body. The state accused Fairchild of fraud and filed a lawsuit against her. Following evidence from another case of chimerism documented in The New England Journal of Medicine in a woman named Karen Keegan, Fairchild was able to secure legal counsel and establish evidence of her biological maternity. A cervical swab eventually revealed Fairchild’s second distinct cell line, showing that she had not genetically matched her children because she was a chimera. Fairchild’s case was one of the first public accounts of chimerism and has been used as an example in subsequent discussions about the validity and reliability of DNA evidence in legal proceedings within the United States.
@stevegis_ssg , I'm always grateful for any critical feedback from people working in this field (such as your good self) about a 2008 essay I wrote on this very topic, "Kudzu and the California Marriage Amendment" (http://linuxmafia.com/faq/Essays/marriage.html), that ended up being one of the most popular pieces I've ever written. All corrections are promptly implemented and acknowledged in the footnotes (only one so far; see footnote 3).
I wrote it as an exercise in "non-rhetoric rhetoric" inspired by one of my favourite authors, John McPhee, who uses that mode of expression to great effect, notably in his superb collection of New Yorker essays The Control of Nature. My target was California Proposition 8, "California Marriage Protection Act", but rather than argue against it in the usual unimaginative (and fruitless) fashion, I tried saying "Suppose you got what you say you want. Would you actually like it?" It turns out, proponents would have been aghast at what they proposed to hammer into the state constitution, as biology would have sabotaged their overly simplistic hopes.
However, my predictions were never put to the test, as the proposition, albeit passed, was swiftly overturned, and the movement behind it became, for now, a dead letter. (As I mention in the essay, those predictions were validated elsewhere.)
Thank you for your work! This isn't even my field; I just do ultrabasic work on transcriptional regulation, mostly in fruit fly muscle and heart development.
OMG! This tiny little world!!!
@stevegis_ssg thank you for this thread!
…I can’t be the first person to want to make a SRY not SRY joke, can I?
@nadege
Please feel free. Someone else collected it on their blog when I first posted it, if that's easier:
@stevegis_ssg
THANK YOU for this. You've articulated a very complex process in a very accessible way.
May I reprint it on my blog? I recently came out to my whole company, including providing a FAQ. This would provide another valuable reference.
@stevegis_ssg
Thanks!
Here's my published blog post.
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