What you carry at this position in your DNA and what research says about it.
Macular Degeneration Risk: 8/10 evidence, 19 publications.
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Sample genotype (not yours): G/G
Typical Macular Degeneration Risk
Ocular health profiles for this baseline genetic makeup show a standard susceptibility to age-related macular degeneration. No inherited protective effect is conferred by this common variant.
What this genotype means: Standard complement C2 protein structure; Typical baseline risk for age-related macular degeneration.
Sample genotype (not yours): C/C
Lower Macular Degeneration Risk
Double copies of the protective C allele are associated with a significantly reduced risk of developing age-related macular degeneration. Strong genetic shielding against complement-driven retinal damage is provided by this genotype.
What this genotype means: Homozygous aspartate at position 318 of complement C2; Significantly reduced risk of age-related macular degeneration.
Sample genotype (not yours): G/C
Inheriting one copy of the protective C allele is associated with a significantly reduced risk of developing age-related macular degeneration. Retinal tissues are shielded from excessive complement-mediated inflammation by this genetic variation.
What this genotype means: Altered complement C2 protein structure; Approximately fifty percent lower risk of age-related macular degeneration.
Gene function and biological role
Gene Function: The C2 gene encodes complement component 2, a key protein in the classical pathway of the complement system. This system is a crucial part of the innate immune response, helping to clear pathogens and cellular debris. Proper regulation of the complement cascade is essential to prevent chronic inflammation in tissues like the retina [1]. Genetic variations in C2 can alter complement activation, which has been linked to inflammatory and degenerative conditions [2].
Variant Impact: A missense mutation in the C2 gene at rs9332739 results in the substitution of the amino acid glutamate with aspartate at position 318 of the complement C2 protein. This molecular alteration is situated within a critical region of the complement protein, potentially influencing its stability or interaction with other cascade components [2]. Large-scale genetic analyses have consistently associated this specific amino acid change with a significantly reduced risk of developing age-related macular degeneration [3]. While some clinical databases classify it as benign because it does not cause complement deficiency, its protective effect against retinal degeneration is well-documented in scientific literature [1].
Key Insight: A single letter change in the C2 gene can cut the risk of age-related macular degeneration by half.
Location: C2. Chromosome 6 · 6p21.33 · 31.9 Mb
Estimated prevalence by population
Global 93.4%; European 91.0%; African 97.6%; East Asian 95.5%; South Asian 89.3%; Americas 95.0%; Ashkenazi 95.0%; Finnish 89.3%; Middle Eastern 95.3%; Amish 97.4%.
Estimated GG genotype frequency.
Global 6.5%; European 8.8%; African 2.4%; East Asian 4.5%; South Asian 10.4%; Americas 5.0%; Ashkenazi 4.9%; Finnish 10.4%; Middle Eastern 4.6%; Amish 2.6%.
Estimated GC genotype frequency.
Global 0.1%; European 0.2%; African < 0.1%; East Asian 0.1%; South Asian 0.3%; Americas 0.1%; Ashkenazi 0.1%; Finnish 0.3%; Middle Eastern 0.1%; Amish < 0.1%.
Estimated CC genotype frequency.
Showing effects for G/G genotype
Organ Systems
Vision & Eye Health
Macular Degeneration. Evidence: 8/10. Source: PMID 22440158. Typical Risk.
Dry Macular Degeneration. Evidence: 8/10. Source: PMID 22705344. Typical Risk.
Wet Macular Degeneration. Evidence: 8/10. Source: PMID 22705344. Typical Risk.
Immunity & Inflammation
Inflammatory & Circulating Protein Markers
Complement Factor B. Evidence: 6/10. Source: PMID 35078996. Higher Levels.
Showing effects for C/C genotype
Macular Degeneration. Evidence: 8/10. Source: PMID 22440158. ~50% Lower Risk.
Dry Macular Degeneration. Evidence: 8/10. Source: PMID 22705344. Lower Risk.
Wet Macular Degeneration. Evidence: 8/10. Source: PMID 22705344. Lower Risk.
Complement Factor B. Evidence: 6/10. Source: PMID 35078996. Typical Levels.
Showing effects for G/C genotype
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Possessing two copies of the common G allele means having the standard glutamate amino acid at position 318 of the complement C2 protein. Standard complement activity is maintained by this genotype, which does not confer the protective advantage against retinal inflammation seen in carriers of the variant allele [1]. Large-scale meta-analyses show that individuals with this baseline genetic profile have a typical risk of developing age-related macular degeneration compared to the general population [2]. Because the complement system plays a major role in clearing cellular debris from the retina, standard complement activity can sometimes lead to low-grade chronic inflammation over time [3]. This inflammatory process can contribute to the gradual breakdown of retinal cells in susceptible individuals. Maintaining regular eye exams and a healthy lifestyle remains important for preserving vision. Protecting the eyes from ultraviolet light and eating a diet rich in antioxidants can also support macular health. Overall, this genotype represents the most common genetic baseline found globally.
Standard complement C2 protein structure; Typical baseline risk for age-related macular degeneration.
Sample genotype: CC (Homozygous)
Two copies of the C allele ensure that all complement C2 proteins produced have the aspartate variant at position 318. This homozygous genotype is relatively rare in most populations but is strongly linked to a decreased susceptibility to age-related macular degeneration [1]. Systematic reviews confirm that carrying the variant allele reduces the odds of developing this progressive eye condition by about half [2]. The altered protein structure likely dampens overactive complement cascade responses that typically damage the macula over time [3]. This protective mechanism is highly consistent across various ethnic groups, particularly in Caucasian populations [2]. Having two copies of the protective allele does not appear to cause complement deficiency or other adverse health conditions. It represents a highly optimized genetic shield against age-related retinal decline. Routine eye examinations are still recommended to monitor overall ocular health. Combining this genetic advantage with a healthy lifestyle provides the best outlook for long-term vision.
Homozygous aspartate at position 318 of complement C2; Significantly reduced risk of age-related macular degeneration.
Sample genotype: GC (Heterozygous)
A single copy of the C allele introduces the aspartate variant into the complement C2 protein, which appears to modulate the classical complement pathway. Multiple clinical studies and meta-analyses have demonstrated that this genotype is associated with an approximate fifty percent reduction in the risk of developing age-related macular degeneration [1]. The protective effect is thought to stem from a subtle reduction in complement-mediated inflammatory processes within the retinal tissue [2]. This shield applies to both dry and wet subtypes of advanced macular degeneration, helping to preserve long-term visual acuity [3]. By dampening the overactive immune responses that typically damage the macula, this variant acts as a natural defense mechanism. The presence of this single protective allele is relatively common in European and South Asian ancestries but less frequent in African populations. While this genetic profile is highly favorable, maintaining routine eye care remains beneficial for long-term vision health. Avoiding modifiable risk factors like smoking can further enhance this natural genetic protection.
Altered complement C2 protein structure; Approximately fifty percent lower risk of age-related macular degeneration.
Variants with shared genetic architecture
rs1042663 · C2 Gene · Chr 6 · Macular Degeneration Risk
rs547154 · C2 Gene · Chr 6 · Macular Degeneration Risk
rs1047286 · C3 Gene · Chr 19 · Macular Degeneration Risk
Gain-of-function mutation in complement C2 protein identified in a patient with aHUS.
Content updated August 2026.
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