What you carry at this position in your DNA and what research says about it.
Eye Color and Skin Cancer: 10/10 evidence, 52 publications.
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Sample genotype (not yours): A/A
Brown Eyes and Higher Glaucoma Risk
Two copies of the A allele lead to brown eyes, darker hair, and skin that tans easily. While this provides excellent protection against skin cancer, it is associated with an increased risk of glaucoma and occupational asthma.
What this genotype means: Brown eyes and darker hair; Lower risk of skin cancer; Increased risk of glaucoma and asthma.
Sample genotype (not yours): A/G
Brown Eyes and Typical Health Risks
Carrying one copy of each allele typically results in brown eyes and medium-to-dark hair and skin. This genotype provides moderate natural UV protection and carries typical baseline risks for skin cancer, asthma, and glaucoma.
What this genotype means: Brown eyes and typical hair color; Typical baseline skin cancer risk; Typical baseline glaucoma and asthma risk.
Sample genotype (not yours): G/G
Blue Eyes and Higher Skin Cancer Risk
Two copies of the G allele lead to blue eyes, blonde or light hair, and fair skin. This lighter pigmentation reduces natural UV protection, leading to an increased risk of skin cancers, including melanoma.
What this genotype means: Blue eyes and lighter hair; Increased risk of skin cancer and sun sensitivity; Lower risk of glaucoma and asthma.
Gene function and biological role
Gene Function: The HERC2 gene encodes a large hect domain and RCC1-like domain-containing protein that functions as an E3 ubiquitin ligase [1]. It plays a critical role in cellular processes, including DNA repair, cell cycle regulation, and pigment determination [1]. Located on chromosome 15, HERC2 contains a highly conserved regulatory region within its intron 86 [1]. This specific region acts as a long-range enhancer that loops over to interact directly with the promoter of the neighboring OCA2 gene [1]. Through this physical interaction, HERC2 controls the expression of OCA2, which is responsible for producing melanin in the eyes, skin, and hair [1].
Variant Impact: The rs12913832 variant is a single nucleotide transition located within intron 86 of the HERC2 gene [1]. This genetic change directly alters the binding affinity of transcription factors, which in turn attenuates chromatin-loop formation with the OCA2 promoter [1]. The ancestral A allele maintains strong enhancer activity, leading to high OCA2 expression and abundant melanin production [1]. Conversely, the derived G allele reduces enhancer activity, significantly decreasing OCA2 expression and resulting in lighter pigmentation [1]. Because of this profound regulatory effect, this single variant is the primary genetic determinant of blue versus brown eye color in human populations [1].
Key Insight: A single genetic letter change inside the HERC2 gene acts as a physical dimmer switch for the neighboring OCA2 gene, single-handedly determining whether a person has blue or brown eyes.
Location: HERC2. Chromosome 15 · 15q13.1 · 28.1 Mb
Origin Story: The blue-eye G allele represents a founder mutation that arose in a single individual near the Black Sea region around 6000 to 10000 years ago, subsequently spreading rapidly through Europe due to positive selection.
Estimated prevalence by population
Global 36.4%; European 5.6%; African 76.4%; East Asian 99.7%; South Asian 82.6%; Americas 57.3%; Ashkenazi 18.3%; Finnish 1.3%; Middle Eastern 62.3%; Amish 14.2%.
Estimated AA genotype frequency.
Global 29.7%; European 36.1%; African 22.0%; East Asian 0.3%; South Asian 16.5%; Americas 36.8%; Ashkenazi 49.0%; Finnish 20.3%; Middle Eastern 33.3%; Amish 47.0%.
Estimated AG genotype frequency.
Global 33.9%; European 58.3%; African 1.6%; East Asian < 0.1%; South Asian 0.8%; Americas 5.9%; Ashkenazi 32.7%; Finnish 78.4%; Middle Eastern 4.4%; Amish 38.8%.
Estimated GG genotype frequency.
Showing effects for A/A genotype
Organ Systems
Pigmentation & Appearance
Eye Color. Evidence: 10/10. Source: PMID 18172690. Brown Eyes.
Sun Sensitivity. Evidence: 8/10. Source: PMID 23548203. Tans Easily.
Hair Color. Evidence: 10/10. Source: PMID 18483556. Darker Hair.
Vision & Eye Health
Glaucoma. Evidence: 9/10. Source: PMID 37386247. Increased Risk.
Respiratory Health
Asthma. Evidence: 4/10. Source: PMID 25918132. ~3.5x Higher Risk.
Cancer & Oncology
Skin Cancer
Skin Cancer. Evidence: 10/10. Source: PMID 23548203. Lower Risk.
Showing effects for A/G genotype
Sun Sensitivity. Evidence: 8/10. Source: PMID 23548203. Moderate Tanning.
Hair Color. Evidence: 10/10. Source: PMID 18483556. Medium to Dark Hair.
Glaucoma. Evidence: 9/10. Source: PMID 37386247. Typical Risk.
Asthma. Evidence: 4/10. Source: PMID 25918132. Typical Risk.
Skin Cancer. Evidence: 10/10. Source: PMID 23548203. Typical Risk.
Showing effects for G/G genotype
Eye Color. Evidence: 10/10. Source: PMID 18172690. Blue Eyes.
Sun Sensitivity. Evidence: 8/10. Source: PMID 23548203. Burns Easily.
Hair Color. Evidence: 10/10. Source: PMID 18483556. Lighter Hair.
Glaucoma. Evidence: 9/10. Source: PMID 37386247. Lower Risk.
Asthma. Evidence: 4/10. Source: PMID 25918132. Lower Risk.
Skin Cancer. Evidence: 10/10. Source: PMID 23548203. Increased Risk.
What this genotype means for the people who carry it
Sample genotype: AA (Homozygous)
Maximum melanin synthesis is promoted by the homozygous A/A genotype through robust enhancer activity at the OCA2 promoter [1]. This genetic profile is strongly associated with brown eyes, dark hair, and skin that tans easily and rarely burns. The abundant pigment provides excellent natural protection against ultraviolet radiation, resulting in a lower risk of skin cancers and uveal melanoma. However, this genotype is linked to an increased susceptibility to other health conditions [2]. Specifically, the A allele is associated with a higher risk of primary angle-closure glaucoma and open-angle glaucoma. Additionally, studies have identified a significant association between this genotype and an increased risk of occupational asthma [3]. Regular eye exams are beneficial for monitoring intraocular pressure and detecting early signs of glaucoma.
Brown eyes and darker hair; Lower risk of skin cancer; Increased risk of glaucoma and asthma.
Sample genotype: AG (Heterozygous)
Melanin production remains relatively high in the presence of a single ancestral A allele [1]. This heterozygous state typically results in brown eye color, darker hair, and skin that tans moderately well under sun exposure. Because the A allele maintains functional enhancer activity, the body produces sufficient protective pigment to shield cells from ultraviolet damage [1]. Consequently, this genotype does not carry the elevated risks of skin cancer or uveal melanoma seen in homozygous G/G individuals. At the same time, the presence of one G allele appears to keep the risks of asthma and glaucoma at typical baseline levels. Overall, this genetic profile represents a balanced baseline across both pigmentation-related and inflammatory health traits.
Brown eyes and typical hair color; Typical baseline skin cancer risk; Typical baseline glaucoma and asthma risk.
Sample genotype: GG (Homozygous)
Lighter pigmentation phenotypes in European populations are primarily driven by the homozygous G/G genotype at this locus [1]. This genetic configuration reduces the expression of the OCA2 gene, leading to a dramatic reduction of melanin in the iris and skin [1]. As a result, there is a 99% probability of having blue eyes, alongside a strong likelihood of blonde hair and fair skin that burns easily in the sun. Because melanin provides a natural shield against ultraviolet radiation, this lack of pigment is associated with an increased risk of cutaneous melanoma and non-melanoma skin cancers. Recent clinical studies have also linked this genotype to a higher risk and worse prognosis of uveal melanoma, a rare eye cancer. Conversely, this genotype is associated with a lower risk of developing certain inflammatory and ocular conditions, such as occupational asthma and glaucoma. Practicing diligent sun protection, including wearing sunscreen and sunglasses, is highly recommended to mitigate these elevated skin and eye cancer risks.
Blue eyes and lighter hair; Increased risk of skin cancer and sun sensitivity; Lower risk of glaucoma and asthma.
Variants with shared genetic architecture
rs1129038 · HERC2 Gene · Chr 15 · Eye Pigmentation and Health
rs1667394 · HERC2 Gene · Chr 15 · Eye Color
rs916977 · HERC2 Gene · Chr 15 · Eye Color
Diversity and scale: Genetic architecture of 2068 traits in the VA Million Veteran Program.
Content updated August 2026.
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