What this means

R160W (C→T at rs1805008) is the second of the three classic MC1R "R" alleles. Like R151C, it produces a partial-loss-of-function receptor that pushes pigment production toward pheomelanin (the red/yellow pigment) and away from eumelanin (brown/black). It shows up at modest frequency across European populations and contributes to the same spectrum of phenotypes: red or auburn hair, fairer skin, freckles, and reduced tanning ability. The trait is most penetrant when paired with another MC1R R allele.

R160W is the second of three classic "red hair" versions of MC1R. Like its sibling R151C, it weakens the receptor a bit, which shifts your pigment production toward the red/yellow side and away from the brown/black side. The effect is most obvious if you carry two copies, or one copy plus another red-hair version: you get the full package of red or auburn hair, fair skin, freckles, and skin that burns rather than tans. One copy on its own is usually subtler.

Caveats

• Single-copy carriers often have only subtle effects (fairer skin, slight freckling).
• The full red-hair phenotype usually requires two R alleles, in any combination.
• MC1R R alleles are well-studied in European cohorts; data in other populations is sparser.
• Hair colour can shift across childhood and adulthood.

References

• Valverde et al. — Variants of the melanocyte-stimulating hormone receptor gene are associated with red hair and fair skin in humans (Nature Genetics, 1995)
• Box et al. — Characterization of melanocyte stimulating hormone receptor variant alleles in twins with red hair (Human Molecular Genetics, 1997)