What you carry at this position in your DNA and what research says about it.
Skin Cancer Risk: 10/10 evidence, 54 publications.
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Sample genotype (not yours): T/T
Typical Skin Cancer Risk
Standard baseline genetic risk for skin cancers and frontal hair loss is typical for this profile.
What this genotype means: Standard baseline risk for melanoma; Standard baseline risk for basal cell carcinoma; Typical susceptibility to frontal hair loss.
Sample genotype (not yours): C/C
Lowest Skin Cancer Risk
Double copies of the protective C allele provide the greatest reduction in risk for skin cancers and frontal hair loss.
What this genotype means: Lowest genetic risk of melanoma; Lowest genetic risk of basal cell carcinoma; Strongest protection against frontal hair loss.
Sample genotype (not yours): T/C
Reduced Skin Cancer Risk
A single copy of the protective C allele is linked to a lower risk of skin cancers and frontal hair loss.
What this genotype means: Moderately lower risk of melanoma; Moderately lower risk of basal cell carcinoma; Reduced susceptibility to frontal hair loss.
Gene function and biological role
Gene Function: The CYP1B1 gene encodes cytochrome P450 1B1, an enzyme involved in metabolizing various compounds, including hormones like estrogen and environmental toxins. It is highly expressed in hormone-sensitive tissues such as the breast, ovaries, and prostate [1]. The enzyme plays a key role in converting estradiol into catechol estrogens, which can influence cellular growth and DNA stability [1]. Variations in this gene can alter enzyme activity or stability, affecting how the body processes these hormones and external carcinogens [2].
Variant Impact: The rs1800440 variant, also known as p.Asn453Ser, is a missense mutation in the CYP1B1 gene that changes the amino acid asparagine to serine at position 453. This specific change alters the stability of the cytochrome P450 1B1 enzyme by accelerating its proteasomal degradation [1]. Consequently, individuals carrying the variant C allele have lower intracellular levels of the enzyme [1]. This reduction in enzyme abundance alters the rate of hormone and xenobiotic metabolism, which influences susceptibility to certain cancers and inflammatory hair loss conditions [3].
Key Insight: The protective C allele causes the CYP1B1 enzyme to break down faster, which unexpectedly lowers the risk of skin cancer and a specific type of hair loss by reducing the accumulation of certain metabolic byproducts.
Location: CYP1B1. Chromosome 2 · 2p22.2 · 38.1 Mb
Estimated prevalence by population
Global 76.3%; European 66.5%; African 93.1%; East Asian 99.1%; South Asian 61.5%; Americas 75.0%; Ashkenazi 70.1%; Finnish 72.6%; Middle Eastern 66.6%; Amish 82.8%.
Estimated TT genotype frequency.
Global 21.6%; European 30.1%; African 6.7%; East Asian 0.9%; South Asian 33.9%; Americas 23.2%; Ashkenazi 27.2%; Finnish 25.2%; Middle Eastern 30.0%; Amish 16.4%.
Estimated TC genotype frequency.
Global 2.1%; European 3.4%; African 0.1%; East Asian < 0.1%; South Asian 4.7%; Americas 1.8%; Ashkenazi 2.6%; Finnish 2.2%; Middle Eastern 3.4%; Amish 0.8%.
Estimated CC genotype frequency.
Showing effects for T/T genotype
Cancer & Oncology
Skin Cancer
Melanoma. Evidence: 9/10. Source: PMID 32341527. Typical Risk.
Basal Cell Carcinoma. Evidence: 10/10. Source: PMID 31174203. Typical Risk.
Organ Systems
Pigmentation & Appearance
Hair Loss. Evidence: 6/10. Source: PMID 30850646. Typical Risk.
Vision & Eye Health
Glaucoma. Evidence: 9/10. Source: PMID 10426814. Typical Risk.
Showing effects for C/C genotype
Melanoma. Evidence: 9/10. Source: PMID 32341527. Lowest Risk.
Basal Cell Carcinoma. Evidence: 10/10. Source: PMID 31174203. Lowest Risk.
Hair Loss. Evidence: 6/10. Source: PMID 30850646. Lowest Risk.
Showing effects for T/C genotype
Melanoma. Evidence: 9/10. Source: PMID 32341527. Reduced Risk.
Basal Cell Carcinoma. Evidence: 10/10. Source: PMID 31174203. Reduced Risk.
Hair Loss. Evidence: 6/10. Source: PMID 30850646. Reduced Risk.
What this genotype means for the people who carry it
Sample genotype: TT (Homozygous)
Standard baseline risk for skin cancers and hair loss is typical for this common genetic profile. Large-scale genome-wide association studies show that the T allele is associated with a standard baseline risk for cutaneous melanoma [1] and basal cell carcinoma [2]. Additionally, this genotype is linked to typical susceptibility to frontal fibrosing alopecia, a form of inflammatory hair loss [3]. Because the T allele produces a more stable version of the CYP1B1 enzyme, it maintains standard rates of hormone and toxin metabolism. This baseline level of enzyme activity does not elevate risk beyond the general population average. Standard preventative measures, such as using sunscreen and monitoring skin changes, remain the primary recommendations.
Standard baseline risk for melanoma; Standard baseline risk for basal cell carcinoma; Typical susceptibility to frontal hair loss.
Sample genotype: CC (Homozygous)
Two copies of the protective C allele offer the strongest genetic protection against cutaneous melanoma [1] and basal cell carcinoma [2]. This genotype leads to the fastest degradation rate of the CYP1B1 enzyme, resulting in the lowest intracellular enzyme levels. These reduced levels significantly lower the risk of developing frontal fibrosing alopecia, a scarring hair loss condition [3]. Although this profile is highly favorable, maintaining standard sun protection remains important for overall skin health. The genetic benefit is particularly pronounced in populations where these skin cancers are more prevalent. Overall, this profile represents a highly protective genetic baseline against hormone- and toxin-related cellular stress.
Lowest genetic risk of melanoma; Lowest genetic risk of basal cell carcinoma; Strongest protection against frontal hair loss.
Sample genotype: TC (Heterozygous)
A single copy of the protective C allele is associated with a moderately reduced risk of developing cutaneous melanoma [1] and basal cell carcinoma [2]. This protective effect stems from the accelerated degradation of the CYP1B1 enzyme, which lowers its intracellular levels. Lower enzyme levels are also linked to a decreased likelihood of developing frontal fibrosing alopecia, an inflammatory hair loss condition [3]. While this genetic profile offers some natural protection, it does not eliminate risk entirely. Standard sun safety practices and routine skin checks are still beneficial. The presence of one C allele represents a favorable genetic variation compared to the common baseline.
Moderately lower risk of melanoma; Moderately lower risk of basal cell carcinoma; Reduced susceptibility to frontal hair loss.
Variants with shared genetic architecture
rs1056836 · CYP1B1 Gene · Chr 2 · Hormone and Drug Metabolism
rs10012 · CYP1B1 Gene · Chr 2 · Estrogen Metabolism
rs1056827 · CYP1B1 Gene · Chr 2 · Breast Cancer Risk
CYP1B1 variants are associated with prostate cancer in non-Hispanic and Hispanic Caucasians.
Catalytic properties of polymorphic human cytochrome P450 1B1 variants.
Content updated August 2026.
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