What are the genetics of freckles?

08 October 2019

FRECKLES-FACE

Freckled face

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Question

What’s the genetics of freckles?

Answer

Adam has a vested interest in this question, so Phil Sansom is here to shed some light onto it...

Phil - Yeah I looked into it. Genetically it's actually, has all these things are not clear cut. So there you go. Freckles are little spots where your melanin is getting produced a lot, a lot, and your melanin is of course, your pigment that makes your skin or your hair darker. And the gene that's responsible in this case is one called MC1R, and that's what controls the protein that goes on the cells that make melanin, the melanocytes, and the protein is what responds to the UV sunlight coming in. It goes: “Ah! I've got to protect the skin!” And then creates this melanin, absorbs all the UV, stops you getting damage to your skin, all sorts of nasty stuff. Now when humans as a big group left Africa, we didn't need all that melanin all across our bodies as much because the sunlight and the UV was less strong. That means in terms of evolution there's less pressure to have the version of the MC1R gene that makes lots of melanin all over your body. When that selection relaxes like that, you get different variants of the gene popping up, so now there's all sorts of different what you call alleles, different versions of that MC1R gene. Here's the caveat, as usual some versions are responsible for freckles. We don't really know why. Which ones? It's a few that are like, linked to it but then there's cases of people in Japan who don't have any of those versions and have freckles anyway that are linked to a different gene. So again a complex picture but we think a large part of it is this MC1R gene. We just don't know why they appear in little patches.

Adam - Stupid science not being clear cut.

Phil -  I'll tell them to get on it. Get them to sort it.

Adam - So does it make you better at dealing with sun or less good at dealing with sun?

Phil - Supposedly in those spots better.

Adam - Okay.

Phil - There's the other thing as well just quickly, which is that it's also linked to red hair, which is the MC1R gene rather is linked to red hair. If you have two copies of a certain allele of the gene you'll have red hair. But if you have one copy of that allele you'll get freckles. So that's a really weird interesting case where the two are linked and it's one allele. That’s the dominant trait on that allele is freckles, because it'll happen even if you only have one copy of it but the recessive trait is red hair which is super strange and also going on a lot in Ireland.

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