i’ve been out of school for a while, but when i was in school, there was no mention of any SRY gene and it’s functions and ability to travel to either X or Y and implications and all of that. It’s a little confusing for me at the moment so could someone explain?
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If you want to fully understand it, you’d need a college level course in genetics and endocrinology. And even then, I wouldn’t expect someone who had these courses to know of every possible exception that can occur naturally.
So as an ELI5: How our body develops depends on a lot of things. At the “visible at certain times with good microscopes” level is chromosome count and length. That’s the level people get to in high school. Scientists who looked closer (aka use analysing methods and computers to visualise things), noticed that chromosomes contain genes and non-coding genom parts. The genes can be “read” and translated into proteins that can have effects on the cell’s functions, its metabolism or it can be released to affect other cells. Some of these are enzymes that change which and how many “sex hormones” are produced, others are the receptors that recognize sex hormones and have an effect on the cell when activated (like on factors that tell the cell how much of another protein to reproduce). Many of the proteins have been identified, but we still don’t the detailed functions of all of them. If you look even closer, the non-coding parts can have effects on how well and how often the coding parts are translated. And then the DNA-strands are rolled up on proteins that can be modified by enzymes, again effecting the rate or ability to read the genes. So the closer you look the more complex it gets.
How our genitalia develop depends on specific genes being present and activated at specific times in our development. And how our brain develops is even more complex. It is influenced by sex hormones, but not as directly as genitalia and it’s not even fully understood by the most knowledgeable scientists in the field.
At any level in this, you can have natural variations (or “mistakes”, but unless they lead to the person not being able to live, I wouldn’t consider it a real mistake). There’s the normal XX and XY; but X, XXY and other variations in chromosome count exist. Then you can have genes translocated onto the “wrong” chromosome. Then there can be mutations in the genes that code for enzymes that influence the hormones, or that code for the hormone receptors, or for other factors that are necessary. These mutations might make no difference, or they make things more effective, or less effective, or completely non-functional. And so on.
In short: Biology is more complex the closer you look at it. Unless you work in the field, you don’t necessarily need to understand every detail, just like you don’t have to be a mechanic to drive a car. But you should listen when people with more background knowledge than you talk about the subject and accept their statements.
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