The MC1R gene turns pheomelanin into eumelanins but there are another kind of pehomelanin called pheochromes. So if a brunette or black person used a cosmetic gene therapy to turn off this gene how would they look like?

Would they became blonde, redhead, with white skin with light coloured eyes?

This is pheomelanin and pheomelanin:

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The are pheochromes:

enter image description here

Since pheomelanins and pheochromes are lighter and varies more in color than eumelanins(which can be only black, brown, grey or yellow), what new kinds of skin, eyes and hair shades could this person opt to change to?

  • $\begingroup$ (1) Can you link to a description of pheochromes? (2) Human skin tone and the amount and relative proportion of phaeo- and eumelanin are polygenic, that is, controlled by multiple genes. (3) You may be interested to know that "white" people come with a very wide variety of skin tones, from very light translucid pigmentation is some nordic populations to quite dark in North Africa, Arabia etc. (4) The MC1R gene is involved in many vital processes; it definitely should not be "turned off". Replaced with one of the alleles associated with red hair, maybe. $\endgroup$
    – AlexP
    Mar 25, 2020 at 23:34
  • $\begingroup$ Honestly, you either should ask this on biology SE or this is an X Y question... $\endgroup$
    – jaskij
    Mar 26, 2020 at 7:02

2 Answers 2


Unknown. But it probably wouldn't be good.

Let's start with the basics. The MC1R gene is responsible for various levels of melatonin compounds within your body. Specifically, it makes the melanocortin 1 receptor in melanocytes, melanocytes being the cells that produce melatonin. When the receptor is triggered, eumelanin is produced. When it's not, pheomelanin is produced. Pheomelanin is generally considered to be the cause of lighter skin colors, as well as lighter eye colors and hair colors. Stop the gene, and you stop the protein. Stop the protein, and you stop eumelanin production.

Except now is when we run into problems. Just adjusting the MC1R gene won't do anything immediately, even if you found a way to adjust the gene without mucking over something else. This is because the melanocytes already exist, so you have to wait for the new batch of melanocytes to take over for this change to be expressed. How long does a melanocytes live for? About 3-5 years. This means that, gradually, over the course of five years, all the subjects melanin levels will be shifted and thus be gently eased into their new body colors. At least, that's the best case scenario.

But we don't get the best case scenario. We currently don't understand exactly how human pigmentation works, so while it's definitely likely that the subject's colors will get lighter, it would be unknown as to what exactly it gets lighter too. It's possible that all you'll trigger is albinoism. Not to mention that the MC1R gene is also linked to immune and inflammatory responses, unknown how, so there's also the potential to trigger a permanent inflammatory response by turning it off. Among other things, included but not limited to, death. Because the body is complicated and screwing with it always had repercussions.

And, lastly, I'm not even sure that turning it off will have the desired effect in melanocytes, because as I said, cells are complicated. I haven't taken an in-depth look at the mechanism MC1R uses, but there's a good chance that taking the trigger protein out won't produce the effect you'd desire. And, as stated in the above paragraph, that's only one of many unknown variables here. If that was the only one, I wouldn't mind going in for a closer look, but it isn't. Tl;dr - the body is complicated, and you likely won't get the result you want.

  • $\begingroup$ Evolution programs like the worlds worst programmer. Spaghetti code and useless things from old versions just left hanging for the right set of conditions to trigger a bug. no wonder it takes so long to develop new features. $\endgroup$
    – IT Alex
    Mar 26, 2020 at 12:25
  • 2
    $\begingroup$ @ITAlex thats what happens when you use a programmer with no forethought. kluges all the way down. $\endgroup$
    – John
    Mar 26, 2020 at 12:40

This is a well-studied gene and a null mutation would result in albinism. As an adult, the skin would fade as the existing cells sloughed off. There would be no visual impairment, as foveal development is a developmental stage (there are Amish people who are technically albinos even though they have brown eyes and dark hair, because they don't produce melanin during foveal development). Albino characteristics haven't been studied in post-development cases except in a very limited way in mice. Tissues that aren't rapidly growing would already have melanin and would be unlikely to be affected. Eye color would stay the same. Null mice had reduced inflammatory responses. There would likely be an increase in sunburn and a serious increase in skin cancer. I suggest going to wikipedia on this one and looking up the Melanocortin 1 receptor.

  • $\begingroup$ Would not ter color become light green or light purple due to the replacement of eumelanin with pheomelanin? $\endgroup$ Apr 2, 2020 at 20:09
  • $\begingroup$ I was assuming from the question of introducing a null mutation. Pheomelanin is a gene variant and if you replaced one with the other the effects would be much milder. most Caucasians express eumelanin, but in much smaller quantities than blacks. The difference is how its expressed, not presence or absence. $\endgroup$
    – DWKraus
    Apr 2, 2020 at 20:24

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