MC1R rs1805006: Red Hair and Skin Pigmentation Genetics
The genetic variant rs1805006, also known as Asp84Glu (D84E), is a missense single nucleotide polymorphism in the MC1R gene on chromosome 16. It alters the melanocortin 1 receptor, influencing melanin synthesis and predisposing carriers to red hair, fair skin, and freckling. Carrying this variant also correlates with heightened sensitivity to ultraviolet radiation and an associated risk for melanoma and non-melanoma skin cancers.
What each genotype means
| Genotype | What the research suggests | Reading |
|---|---|---|
| CC | You carry two copies of the ancestral reference allele. This genotype is associated with normal melanocortin 1 receptor signaling and a typical baseline capacity to produce protective eumelanin, without an inherited predisposition to red hair from this locus. | Informational |
| CA (or CG) | You carry one copy of the variant allele alongside a standard allele. Heterozygous carriers frequently display intermediate traits such as lighter skin pigmentation, freckles, or fair hair, and are recognized carriers of the red hair phenotype with modestly elevated UV sensitivity. | Higher attention |
| AA (or compound heterozygous) | You carry two copies of the variant allele (or this variant paired with another MC1R loss-of-function allele). This genotype is strongly associated with the classic red hair phenotype, very pale skin that burns easily in sunlight, and higher relative risk for ultraviolet-mediated skin damage. | Higher attention |
Genetic Location and Molecular Identity
The single nucleotide polymorphism rs1805006 is situated in the single coding exon of the melanocortin 1 receptor gene, designated MC1R, located on chromosome 16 at band 16q24.3. At the molecular level, this variation represents a base change from the ancestral cytosine (C) nucleotide to an adenine (A) or guanine (G) allele, most commonly cataloged as a C-to-A transversion. This nucleotide shift alters codon 84 of the protein sequence, replacing an aspartic acid residue with glutamic acid, an alteration historically denoted as Asp84Glu or D84E. Because MC1R encodes a seven-transmembrane G-protein coupled receptor critical for skin and hair biology, changing this amino acid alters receptor conformation and signaling capacity.
Biological Mechanism of the MC1R Receptor
The MC1R protein functions as a central switch in specialized cells known as melanocytes, which produce melanin pigments. Under standard physiological conditions, activation of MC1R by alpha-melanocyte-stimulating hormone elevates intracellular cyclic AMP, prompting melanocytes to synthesize eumelanin, a dark brown-to-black pigment that absorbs and scatters ultraviolet radiation. When loss-of-function variants like rs1805006 occur, receptor signaling diminishes. This functional impairment shifts cellular melanin synthesis toward pheomelanin, a reddish-yellow, sulfur-containing pigment that provides minimal protection against ultraviolet light and can generate reactive oxygen species upon sun exposure, elevating oxidative stress in skin tissue.
Clinical and Phenotypic Associations
In human genetic literature, rs1805006 is traditionally classified as an 'R' allele—a designation reserved for variants with strong penetrance for the red hair color phenotype. Genome-wide association studies catalog rs1805006 among key loci influencing red versus brown or black hair, fair complexion, freckling tendency, and sun-burning susceptibility. Because pheomelanin provides inferior shielding against cellular DNA damage caused by solar radiation, clinical databases like ClinVar record rs1805006 under hereditary susceptibility to cutaneous malignant melanoma and non-melanoma skin neoplasms. However, because skin cancer is multifactorial, this variant confers statistical risk rather than an inevitable medical diagnosis.
Population Distribution and Ancestral Patterns
The rs1805006 variant displays substantial divergence across global populations. It is observed primarily in populations of European heritage, particularly those with ancestry traced to northern, western, and central Europe, where minor allele frequencies commonly range between 0.005 and 0.05, and reach up to 0.10 in targeted cohort subsets. Outside of individuals with European lineage, the alternative allele is exceedingly rare or virtually absent in indigenous African, East Asian, and Native American reference cohorts within large sequencing projects like gnomAD. This population distribution mirrors positive selection and drift events that shaped northern European pigmentary adaptation.
Actionable Insights and Preventive Takeaways
Knowing one's rs1805006 genotype provides an understanding of personal pigmentation genetics and UV sensitivity, but it does not represent a diagnostic test. Regardless of whether an individual carries the common ancestral genotype or the variant allele, standard ultraviolet radiation protection remains crucial. Broad-spectrum sunscreen, protective clothing, and routine self-examinations for atypical moles help mitigate skin cancer risk across all skin types. Genetic test results should never replace professional medical evaluations, and any changing or irregular skin lesions should be evaluated promptly by a dermatologist or primary care provider.
How common is this variant?
The rs1805006 variant is predominantly found in populations of European descent, where the minor allele frequency typically ranges from 0.01 to 0.05 (reaching up to 0.10 in selected regional cohorts), while remaining rare or unobserved in East Asian and African ancestries.
Frequently asked questions
Does having the rs1805006 variant guarantee I will have red hair?
No, carrying the rs1805006 variant does not guarantee red hair. Red hair is largely an inherited recessive trait that typically requires two loss-of-function MC1R variants (either homozygous or compound heterozygous), though single-copy carriers often exhibit lighter hair or freckles.
Does rs1805006 cause melanoma?
The rs1805006 variant does not directly cause melanoma, but it is statistically associated with an increased susceptibility. Because the altered receptor leads to more pheomelanin and less protective eumelanin, skin cells have less natural protection against ultraviolet damage, increasing overall cancer risk.
Can people without red hair carry rs1805006?
Yes, many individuals who do not have red hair carry a single copy of rs1805006. As heterozygous carriers, they may have brown or blonde hair while still inheriting related traits such as fair skin, sun sensitivity, or freckling.
How does rs1805006 affect daily sun protection needs?
Carriers of this variant generally burn more easily and tan less readily due to reduced eumelanin synthesis. Dermatologists recommend diligent sun protection for individuals with MC1R variants, including the use of broad-spectrum SPF 30+ sunscreen, UV-blocking hats, and shade.
Sources & further reading
Educational information only, last refreshed 9/6/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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Melanocortin 1 receptor variant altering receptor activity, contributing to pale complexion, increased freckling, and altered tanning capacity.
Common missense polymorphism (p.Arg163Gln) conferring increased risk of cutaneous melanoma and basal cell carcinoma.
A well-characterized missense substitution (Arg142His) in MC1R strongly associated with red hair, pale skin, and increased freckling index.
A missense variant (Val60Leu) in the melanocortin 1 receptor gene associated with red hair, fair skin phenotype, freckling, and altered tanning response.
Encodes the Arg160Trp missense change that contributes strongly to pale skin, freckling, and red hair in ancient northwestern European lineages.
Regulatory MC1R intronic variant associated with severe facial sun damage, solar lentigines, and perceived photo-age acceleration.