I remember in high school learning about Punnet squares; people with dark hair had the dominant hair color gene, and the redhead 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 and may also possibly impact the way you respond to certain analgesics.
Hair Color Genes: What Makes it Red?
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 red hair and skin to be more photosensitive.
Melanoma Risk for Red Hair:
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 are genetic:
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 in people: MC1R function
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’.
MC1R & Redhair Genotype Report:
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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. Additionally, less common MC1R mutations are not included in 23andMe or AncestryDNA data but can cause 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 rs1805009 or 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 rs1805009 is — or for i3002507 is —.
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.
While everyone thinks about hats as a way to decrease sun exposure, there are also new lightweight fabric shirts that are made for keeping cool while blocking UV radiation.
Analgesics and Pain Relief:
Kappa-opioid analgesics may act differently in women with red hair. If you need analgesics (pain medication) before surgery or a dental procedure, you may want to talk with your doctor about whether you will need more pain relief. Research has shown that people with red hair often need a higher dose to relieve pain – depending on the type of analgesic used.[ref]
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