What you carry at this position in your DNA and what research says about it.
Breast and Ovarian Cancer Risk: 9/10 evidence, 4 publications.
You're viewing every possible genotype for this variant.
None of these is your result. Use the genotype toggle to compare them, then sign up and upload your DNA to see which one is yours.
Sample genotype (not yours): G/G
Typical Hereditary Cancer Risk
Two normal copies of the BRCA1 gene are present. This genotype is associated with a typical baseline risk of breast, ovarian, and pancreatic cancers.
What this genotype means: Typical baseline risk of breast cancer; Typical baseline risk of ovarian cancer; Typical baseline risk of pancreatic cancer.
Sample genotype (not yours): A/A
Extremely Rare Biallelic BRCA1 Variant
Two copies of the pathogenic BRCA1 variant are present. This genotype is typically embryonic lethal or leads to a severe developmental disorder called Fanconi anemia.
What this genotype means: Severe risk of Fanconi anemia; High risk of early-onset childhood cancers; Typically embryonic lethal.
Sample genotype (not yours): G/A
Significantly Elevated Hereditary Cancer Risk
One copy of the pathogenic BRCA1 variant is present. This significantly increases the lifetime risk of developing breast, ovarian, and pancreatic cancers.
What this genotype means: Significantly increased lifetime risk of breast cancer; Significantly increased lifetime risk of ovarian cancer; Increased risk of pancreatic cancer.
Gene function and biological role
Gene Function: The BRCA1 gene encodes a tumor suppressor protein that plays a critical role in maintaining genomic stability. It is involved in repairing damaged DNA, specifically double-strand breaks, through the homologous recombination pathway [1]. When functioning normally, the BRCA1 protein helps prevent cells from growing and dividing too rapidly or in an uncontrolled way [1]. Mutations in this gene significantly impair DNA repair, leading to an accumulation of genetic errors and a drastically increased risk of developing cancers [2].
Variant Impact: The rs80357131 variant, also known as p.Gln855Ter or Q855X, is a single nucleotide change from G to A in the BRCA1 gene. This mutation introduces a premature stop codon at amino acid position 855, replacing a glutamine residue with a stop signal. The resulting truncated protein is missing critical functional domains required for DNA repair [1]. This loss-of-function variant is highly pathogenic and is strongly associated with hereditary breast and ovarian cancer syndrome [2].
Key Insight: A single copy of this variant significantly increases breast and ovarian cancer risk, while carrying two copies is typically embryonic lethal or causes a severe developmental disorder called Fanconi anemia.
Location: BRCA1. Chromosome 17 · 17q21.31 · 43.1 Mb
Estimated prevalence by population
No frequency data available
This variant is not present in the gnomAD database.
Showing effects for G/G genotype
Cancer & Oncology
Breast Cancer
Breast Cancer. Evidence: 9/10. Source: PMID 12673801. Typical Risk.
Gynecological Cancers
Ovarian Cancer. Evidence: 9/10. Source: PMID 12673801. Typical Risk.
Gastrointestinal Cancers
Pancreatic Cancer. Evidence: 9/10. Source: PMID 12673801. Typical Risk.
Rare Genetic Disorders
Inherited Metabolic Disorders
Fanconi Anemia. Evidence: 9/10. Source: PMID 16267036. Typical Risk.
Showing effects for A/A genotype
Breast Cancer. Evidence: 9/10. Source: PMID 12673801. Significantly Higher.
Ovarian Cancer. Evidence: 9/10. Source: PMID 12673801. Significantly Higher.
Pancreatic Cancer. Evidence: 9/10. Source: PMID 12673801. Increased Risk.
Fanconi Anemia. Evidence: 9/10. Source: PMID 16267036. Extremely High Risk.
Showing effects for G/A genotype
Fanconi Anemia. Evidence: 9/10. Source: PMID 16267036. Healthy Carrier.
What this genotype means for the people who carry it
Sample genotype: GG (Homozygous)
Two functional copies of the BRCA1 gene allow the body to produce full-length, active tumor suppressor proteins [1]. These proteins are essential for repairing double-strand DNA breaks and maintaining genomic integrity [1]. Lacking the pathogenic p.Gln855Ter mutation means there is no elevated hereditary risk of breast or ovarian cancer from this specific genetic location [2]. Normal DNA repair mechanisms remain fully intact to protect cells from accumulating cancer-causing mutations. However, general lifestyle factors, environmental exposures, and other genetic variants still contribute to overall cancer risk. Maintaining a healthy lifestyle further supports the body's natural cellular defense systems.
Typical baseline risk of breast cancer; Typical baseline risk of ovarian cancer; Typical baseline risk of pancreatic cancer.
Sample genotype: AA (Homozygous)
Biallelic inheritance of a pathogenic BRCA1 nonsense mutation is extremely rare because complete loss of BRCA1 function is generally incompatible with embryonic survival [1]. In rare viable cases, carrying two copies of this variant leads to Fanconi anemia subtype S, a severe chromosomal instability syndrome [1]. This condition is characterized by growth failure, microcephaly, developmental delay, and a high predisposition to early-onset childhood cancers [1]. Normal cellular DNA repair is profoundly compromised, leading to rapid accumulation of chromosomal breaks.
Severe risk of Fanconi anemia; High risk of early-onset childhood cancers; Typically embryonic lethal.
Sample genotype: GA (Heterozygous)
A single copy of this stop-gain mutation results in a truncated, non-functional BRCA1 protein [1]. This loss of function impairs the homologous recombination pathway, making cells less capable of repairing DNA damage [1]. Consequently, a significantly elevated lifetime risk of hereditary breast and ovarian cancer syndrome is associated with this genotype [2]. Early-onset breast cancer is also strongly predicted by this genetic change [3]. Cells carrying this mutation are more vulnerable to secondary genetic hits that can trigger tumor development.
Significantly increased lifetime risk of breast cancer; Significantly increased lifetime risk of ovarian cancer; Increased risk of pancreatic cancer; Healthy carrier of recessive Fanconi anemia.
Variants with shared genetic architecture
rs142074233 · BRCA1 Gene · Chr 17 · Breast Cancer Risk
rs16941 · BRCA1 Gene · Chr 17 · Breast Cancer Risk
rs16942 · BRCA1 Gene · Chr 17 · Breast Cancer Risk
BRCA1 and BRCA2 mutation analysis in breast-ovarian cancer families from northeastern Poland.
Prediction of pathogenic mutations in patients with early-onset breast cancer by family history.
Content updated August 2026.
ReadYourDNA provides educational interpretation of DNA data you already have. It is not diagnostic, not a substitute for professional medical advice, diagnosis, or treatment, and is not intended to diagnose, treat, cure, or prevent any disease. Talk to a clinician before acting on any result.
Raw DNA Data Reports for 23andMe & AncestryDNA · About ReadYourDNA · FAQ · Methodology & Science · Pricing · Support and complaints · Legal & Contact · Health Traits · Pharmacogenomics · Carrier Status · Variant Explorer · The Human Karyotype · Privacy Policy · Terms of Service · Accessibility · Consumer Health Data Privacy · Your Privacy Choices · Editorial Standards · Your Data, Checkable · Sample Report · ReadYourDNA and Promethease compared · What is inside a 23andMe raw data file · What is inside an AncestryDNA raw data file · What a chatbot can and cannot do with your raw DNA file · Where a raw DNA file can still be uploaded in 2026
Written, maintained and operated by Martin Pechhacker, sole proprietor, Vienna, Austria. Trade register GISA 40064420. support@readyourdna.com