BRCA1 rs2227945: What Your Genotype Means
The rs2227945 variant is a single nucleotide polymorphism located within the BRCA1 gene. It has been identified in research as one of several genetic markers that may contribute to a minor, cumulative increase in breast cancer risk.
What each genotype means
Typical risk profile
This genotype represents the common version of this variant. Research suggests this specific genetic sequence does not contribute to the minor increased risk associated with the alternative allele.
This is the most common genotype observed in most global populations.
Slightly elevated risk
Carrying one copy of the G allele is associated with a minor increase in the cumulative risk for breast cancer. This association is based on large-scale population studies, though the individual impact remains limited.
This heterozygous genotype is found in a significant portion of the population, consistent with a minor allele frequency of approximately 1.1%.
Slightly elevated risk
Carrying two copies of the G allele is associated with a minor increase in the cumulative risk for breast cancer. While identified in genome-wide association studies, this variant's contribution to overall risk is considered small and should be viewed in the context of your broader health history.
This homozygous genotype is relatively rare, occurring in a small percentage of the population consistent with the reported minor allele frequency.
Understanding the rs2227945 Variant
The rs2227945 variant is a specific change in the DNA sequence located on chromosome 17. In the context of human genetics, a single nucleotide polymorphism, or SNP, represents a variation at a single position in the DNA building blocks. This particular SNP sits within the BRCA1 gene, a region of the genome that has been extensively studied for its role in cellular health. While many people associate BRCA1 primarily with rare, high-risk mutations that significantly increase the likelihood of developing certain cancers, rs2227945 is a common variant. It is not a high-penetrance mutation, but rather a subtle difference in the genetic code that researchers track to understand how small variations across the population might influence health outcomes over time.
The Role of the BRCA1 Gene
The BRCA1 gene provides instructions for making a protein that acts as a tumor suppressor. This protein is essential for repairing damaged DNA, which helps maintain the stability of a cell's genetic information. When DNA damage is repaired correctly, cells can grow and divide in a controlled manner. If the BRCA1 protein is absent or not functioning properly, DNA damage may accumulate, which can sometimes lead to the uncontrolled cell growth characteristic of cancer. While pathogenic mutations in BRCA1 are well-known for their strong impact on cancer risk, common variants like rs2227945 are thought to have much more modest effects. These variants do not typically cause the gene to stop working, but they may slightly alter how the gene is expressed or how the resulting protein functions in the body.
Research and Evidence Strength
The association between rs2227945 and breast cancer risk is considered to be of limited strength. Scientific literature has categorized this SNP as one of approximately 25 variants that, when considered together, may contribute to a cumulative, albeit minor, increase in breast cancer susceptibility. It is important to note that the effect of any single common variant like rs2227945 is generally very small compared to other factors such as family history, lifestyle, and rare high-risk mutations. Because the individual impact is so low, it is difficult to isolate the effect of this specific SNP in clinical settings. Current research emphasizes that these findings are statistical associations observed in large population studies rather than direct indicators of an individual's personal health outcome.
Population Frequency
The rs2227945 variant is found across various human populations, with a Global Minor Allele Frequency (GMAF) reported at approximately 0.01102. This frequency indicates that the variant is relatively uncommon but present in the general population. Because allele frequencies can vary significantly between different ancestral groups, researchers often look at large-scale databases like gnomAD to understand how common a variant is globally. The low frequency of this specific allele means that most individuals will carry the more common version of the DNA sequence at this position. Understanding these frequencies is a fundamental part of genetic research, as it helps scientists determine whether a specific variant is rare or common and how it might be distributed across different parts of the world.
Interpreting Your Genetic Information
If you have received information about your rs2227945 genotype, it is essential to view it within the context of your overall health. This variant is not a diagnostic tool, and it cannot predict whether an individual will develop breast cancer. Genetic risk is complex and involves the interplay of many different genes, environmental factors, and personal history. Because the evidence linking this SNP to health outcomes is limited and the effect size is minor, this information is generally not used to guide clinical decision-making or medical interventions. If you have concerns about your personal or family history of cancer, the most appropriate step is to consult with a healthcare provider or a certified genetic counselor. They can help you interpret your genetic data accurately and discuss appropriate screening or risk-assessment strategies based on your unique medical profile.
How common is this variant?
The rs2227945 variant has a Global Minor Allele Frequency (GMAF) of 0.01102, indicating it is a relatively uncommon genetic variation across global populations.
Frequently asked questions
Does having the rs2227945 variant mean I will get breast cancer?
No. This variant is associated with a very minor, cumulative increase in risk and is not a diagnostic indicator. Most people who carry this variant will never develop breast cancer.
Should I be worried about my rs2227945 genotype?
There is no reason for concern based on this variant alone. It is a common genetic marker with a very small effect size that is not used for clinical diagnosis or individual risk prediction.
Can I change my risk if I have this variant?
Genetic variants are fixed at birth. However, you can manage your overall health through lifestyle choices and regular screenings recommended by your doctor, which are far more impactful than any single SNP.
Where can I get more information about my genetic risk?
If you have concerns about your health or family history, you should speak with a primary care physician or a genetic counselor. They can provide personalized guidance based on your full medical history.
Sources & further reading
Educational information only, last refreshed 9/18/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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This variant is classified as likely pathogenic for BRCA1-related cancer predisposition based on multifactorial likelihood analysis and functional assay data.
This variant is a pathogenic mutation associated with hereditary breast and ovarian cancer syndrome, with clinical significance supported by multiple submitters and expert curation.
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This variant (p.Arg1699Trp) is a well-documented pathogenic variant in the BRCA1 gene associated with increased risk of hereditary breast and ovarian cancer.
This rare variant has been recently annotated in clinical databases as a potential contributor to hereditary breast and ovarian cancer risk.