The ‘redhead’ gene

I remember in high school learning about Punnet squares; people with dark hair had the dominant hair color gene and red hair gene was recessive. It turns out it isn’t nearly as simple as having a red hair gene or a brown hair gene. (Nor is there a blue eye gene or a short gene…)  Instead, certain variants in the MC1R gene control the red pigmentation in the hair.

The genetic variant that causes red shades of hair impacts other aspects of our health as well.  Carrying the variant can cause an increased risk of melanoma as well as possibly impacting the way you respond to certain analgesics.

Hair color genetics:

There are two types of pigments for hair color: eumelanin and pheomelanin.

  • Eumelanin comes in either black or brown, with varying amounts responsible for ranges of hair color from blond (low eumelanin) to black (high eumelanin).
  • Pheomelanin contributes to red and orange coloring.
  • Most people have both eumelanin and pheomelanin, and the varying amounts of each protein contribute to the wide range of hair colors that people naturally have.

The MC1R (melanocortin-1 receptor) gene controls how much melanin vs pheomelanin is produced in the skin and hair.  Genetic variants of MC1R produce different amounts of pheomelanin, with increased pheomelanin causing the skin to be more photosensitive along with red hair.

Melanoma Risk:

The variant forms of MC1R are also thought to not activate DNA repair as well as the more common MC1R form.  This leads to higher rates of mutations in the DNA of skin cells, possibly leading to skin cancer. [ref]

The link to melanoma is well established for the common MC1R variants that cause red hair, but what people may not realize is that carrying one copy of the variant also doubles the risk of melanoma.[ref]

Freckles and moles:

The MC1R gene is also linked to freckles and more moles on the skin.[ref] Additionally, one MC1R variant (rs1805008) has also been tied to an increased risk of Parkinson’s disease.[ref]

Beyond red hair:

MC1R isn’t just a human-specific gene; it causes pigmentation variation in animals from chickens to goats to carp. It is also thought to be involved in the browning reaction of cut apples being exposed to air.

Beyond the ‘red hair’ gene, predicting hair color from genetic data can be tricky.  Here is a great article on 124 genes that influence hair color.

Additionally, a lot of men who carry one copy of the MC1R variant may notice that their beard hair is reddish, especially in the sunlight. The Irish call this a ‘gingerbeard’.


Genetic variants of the MC1R gene:

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Note that people who are compound heterozygous – carrying one copy of the variant in two different spots – can also have red hair.

Check your genetic data for rs1805008 (23andMe v4, v5; AncestryDNA):

  • T/T: red hair possible; increased risk of melanoma, pos. increased risk of Parkinson’s[ref][ref][ref]
  • C/T: increased risk of melanoma
  • C/C: typical

Members: Your genotype for rs1805008 is .

Check your genetic data for rs1805007 (23andMe v4,v5):

  • T/T: red hair is likely; increased risk of melanoma,[ref] increased response to kappa-opioid analgesics in women [ref];
  • C/T: higher risk of melanoma
  • C/C: typical

Members: Your genotype for rs1805007 is .

Check your genetic data for rs1805006 (23andMe v4,):

  • A/A: red hair is likely; increased risk of melanoma[ref]
  • A/C: higher risk of melanoma
  • C/C: typical

Members: Your genotype for rs1805006 is .

Check your genetic data for i3002507 (23andMe v4, v5):

  • C/C: red hair possible, increased risk of melanoma
  • C/G: higher risk of melanoma
  • G/G: typical

Members: Your genotype for i3002507 is .

Check your genetic data for rs2228479 (23andMe v4, v5; AncestryDNA):

  • A/A: red or blond hair possible, increased Alzheimer’s risk [ref][ref] perhaps not increasing the risk of melanoma[ref]
  • A/G: typical
  • G/G: typical

Members: Your genotype for rs2228479 is .


Lifehacks:

Common sense dictates watching your sun exposure and avoiding a sunburn if you carry one of the risk variants listed above for melanoma.

While you need a certain amount of sun for vitamin D production, knowing when to cover up or put on sunscreen is important. In other words – avoid staying in the sun to the point that your skin starts to turn pink.

Sunscreens:

So what should you look for in sunscreen if you are going to use one? The Environmental Working Group (EWG) has a whole guide to sunscreens and includes research on which ingredients are concerning. High on the list of possibly hazardous ingredients are oxybenzone and octinoxate, both of which penetrate through the skin and have hormone-like activity in the body.

A few sunscreens ranked as having better ingredients on EWG include: Kabana Organic Skincare Green Screen Sunscreen Lotion, Blue Lizard Australian Sunscreen, and Badger Clear Zinc Sunscreen Cream. You can find the full list here.

Cover up

While everyone thinks about hats as a way to decrease sun exposure, there are also new light weight fabric shirts that are made for keeping cool while blocking UV radiation.


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Author Information:   Debbie Moon
Debbie Moon is the founder of Genetic Lifehacks. She holds a Master of Science in Biological Sciences from Clemson University and an undergraduate degree in engineering. Debbie is a science communicator who is passionate about explaining evidence-based health information. Her goal with Genetic Lifehacks is to bridge the gap between the research hidden in scientific journals and everyone's ability to use that information. To contact Debbie, visit the contact page.