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March 2019
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Aerden [userpic]
Wizarding Genetics (Harry Potter)

I think I figured out wizarding genetics tonight!

I have been wracking my brain for years, trying to figure out wizarding genetics. It never made sense to me how one could have both muggleborn wizards and squibs. I always figured that the gene for magic was a recessive trait, which meant that it should be impossible for two wizards to ever have a squib child.

Tonight, I found out how it works. Magic is genetically inherited in two (and possibly more) ways.

I was reading about a genetic condition called Waardenburg syndrome, which causes deafness and hypopigmentation of the skin, among other things.

Waardenburg's occurs in several types, Some types of it are autosomal-recessive, which means that a child must have two copies of the gene to be affected, and children of either sex can be affected. Other types of it are autosomal-dominant, which means that a child of either sex will get Waardenburg's even if he has only one copy of the gene for it from his parents.

I haven't totally worked out the genetics, but for me, this somewhat explains the squibs and muggleborns puzzle. I don't know if Rowling knew about the genetics of Waardenburg's, but this is just amazing and wonderful to me.

If I'm right, and the gene for magic is recessive in muggleborns and dominant in squibs (who don't inherit the gene at all), then the DE are wrong. Muggleborn wizards have to be, in fact, pureblooded in a manner of speaking, since the only way they can acquire magic is if they have two copies of the gene.

Current Mood: accomplishedaccomplished

Two other factors to consider: mixed penetrance (same genes, different effects), and spontaneous mutations. Non-harmful mutations tend to have very high rates of spontanteous mutation, as do mutations that cause harm only after the reproductive years like Marfan's. So...other genes may effect whether the magic genes are expressed, and both magical and nonmagical genes may spontaneously occur. Still, as a general answer, I like this.

Hope--Mixed penetrance is something I didn't get to in high school or even college biology; all I had was Mendelian traditional genetic grids, which I've since learned is just the very basics of it and isn't even always right. I heard something about the original observations themselves being skewed by the people making them--Mendel's assistants? Maybe that was just hearsay.

But yes, it's also possible that inheriting magic is sort of like inheriting hair color, which I understand is caused by several genes acting together. I'd love to learn more about this.

I also wondered if, in the case of magic, it might be possible for a person to possess both the gene set responsible for recessive inheritance of magic and the gene set responsible for dominant inheritance of it. But if that were the case, I suspect we'd see a lot more wizards in the Potterverse population than there are.

A handy chart of the three-way genes.

I was contemplating it recently as well and came up with a chart of the various pairings and what they result in, assuming one gene location with three traits to work with: