All this stuff about ‘oh women are XX’, ‘oh men are XY’ is really pissing me off. And women are now being tested for a Y chromosome gene before competing at the Olympics.
And yeah this is a failure of basic education, but I work in genetics, my PhD is in genetics, I’ve worked in clinical genetics. Genetics and ‘Sex’ is so so so much more than 46,XX and 46,XY, genetics is wild and interesting and god I wish it wasn’t concentrated down into that.
There are so many people out there who present as women and are walking around with just 45,X or 47,XXX, a significant number without even realising! Some people are born with some cells with XX, some with just X, some with XY and literally myriad combinations and proportions! And even if someone has 90% XY cells and 10% X they may still present phenotypically female!
The proportion of how many ‘male’ cells and ‘female’ cells measured in the blood doesn’t even reliably predict how someone develops! (This is called mosaicism and I’ve literally done a research project on it)
Some people have 46,XY but because of so many reasons like genes (SRY), or hormone production or ability to respond to hormones - like being completely insensitive to testosterone - their body presents as phenotypically female.
Sometimes the Y chromosome is inherently unstable and literally falls off as you get older!!! So you have people walking around with 45,X cells when earlier in life they had 46,XY!
TLDR; man = XY, woman = XX is a VAST oversimplification.
