MC1R
A gene encoding the melanocortin 1 receptor, which regulates pathways involved in melanin production. Its variants are associated with differences in hair and skin color and responses to ultraviolet radiation.
Natural redheads may need more anaesthetic. A 2004 study found people with the MC1R gene variant behind red hair needed up to 20% more, as the variant shifts hormones governing pain response. But other studies disagree, so it's too soon to generalise.
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