BRCA1 is a gene that every person has. Its job is to help repair damaged DNA inside your cells, acting as a critical safeguard against cancer. When someone refers to “having the BRCA1 gene,” they typically mean they carry a harmful mutation in that gene, one that disables its protective function and significantly raises the lifetime risk of breast, ovarian, and several other cancers.
What the BRCA1 Gene Does
Every time your cells divide, their DNA can sustain damage. One of the most dangerous types is a double-strand break, where both strands of the DNA helix snap. Left unrepaired, these breaks can lead to mutations that allow cells to grow uncontrollably.
The protein produced by the BRCA1 gene is a central player in a repair process called homologous recombination. Think of it like a copy-and-paste function: the cell uses the intact copy of the chromosome as a template to accurately rebuild the broken section. BRCA1 helps coordinate this repair, recruiting other proteins to the damage site so the fix is precise. When the gene is working normally, it acts as a tumor suppressor, catching and correcting DNA errors before they spiral into cancer.
A harmful BRCA1 mutation means this repair system is compromised. Cells accumulate DNA errors faster than they can fix them, and over time, some of those errors hit genes that control cell growth. That’s the path from a faulty repair gene to cancer.
How BRCA1 Mutations Are Inherited
BRCA1 mutations follow an autosomal dominant inheritance pattern. That means you only need to inherit one altered copy of the gene, from either parent, to carry the increased risk. If a parent has a BRCA1 mutation, each of their children has a 50 percent chance of inheriting it.
Both men and women can carry and pass on the mutation. A father with a BRCA1 mutation is just as likely to transmit it to his children as a mother is. This is worth knowing because family history discussions often focus on the maternal side, which can cause people to overlook risk inherited from their father.
Who Is Most Likely to Carry a Mutation
BRCA1 mutations occur across all ethnic groups, but they are significantly more common in certain populations. People of Ashkenazi Jewish descent have a notably higher prevalence of BRCA1 variants compared to the general population. Among Ashkenazi Jewish individuals with breast cancer who test positive for BRCA1 or BRCA2, roughly 71 percent carry the BRCA1 variant specifically.
Other populations with elevated rates include people of Norwegian, Dutch, and Icelandic ancestry, though the Ashkenazi Jewish population is the most studied. In the general population, roughly 1 in 300 to 1 in 500 people carry a harmful BRCA1 or BRCA2 mutation.
Cancer Risks for BRCA1 Carriers
The numbers are sobering. Women who inherit a harmful BRCA1 mutation face a lifetime breast cancer risk of roughly 55 to 72 percent, compared to about 13 percent for the general population. The risk of ovarian cancer (which includes fallopian tube and primary peritoneal cancers) is 39 to 58 percent, versus roughly 1.2 percent for the average woman. These are lifetime risks, meaning they represent the cumulative probability by age 70 to 80.
BRCA1 mutations also raise the risk of other cancers, though to a lesser degree. Men with BRCA1 mutations face a moderately increased risk of prostate cancer. There are also associations with pancreatic cancer in both sexes. BRCA1-related breast cancers tend to be “triple-negative,” a subtype that doesn’t respond to hormone-based treatments and historically has been harder to treat.
Testing and Screening
Genetic testing for BRCA1 involves a blood or saliva sample. It’s typically recommended for people with a strong family history of breast or ovarian cancer, a family member with a known BRCA mutation, or ancestry in a high-risk group. Genetic counseling before and after testing helps you understand what the results mean for you and your family.
If you test positive, screening starts earlier and is more intensive than standard guidelines. Current recommendations call for breast awareness beginning at age 18 and clinical breast exams every 6 to 12 months starting at age 25. Annual breast MRI is recommended from age 25 to 75, and annual mammography (often with tomosynthesis, a type of 3D imaging) starts at age 30. Staggering the MRI and mammogram six months apart means you’re getting some form of imaging every six months, which improves the chance of catching cancer early.
Options for Reducing Risk
Carriers have several strategies beyond surveillance. The most significant risk reduction comes from preventive surgery. Removing both ovaries and fallopian tubes has been shown to lower the risk of ovarian and fallopian tube cancer by 80 to 90 percent and the risk of breast cancer by about 50 percent in BRCA mutation carriers. This surgery triggers early menopause, so the timing is a personal decision that balances cancer risk against quality-of-life factors like fertility, bone health, and menopausal symptoms. Many carriers choose this option after completing their families, often in their late 30s or 40s.
Preventive mastectomy is another option that reduces breast cancer risk by roughly 90 percent or more. Some carriers opt for risk-reducing medications instead, which can lower breast cancer risk but are less effective than surgery. The right choice depends on your specific mutation, family history, age, and personal priorities.
Treatment When Cancer Develops
Ironically, the same DNA repair defect that makes BRCA1 carriers more vulnerable to cancer also creates a treatment advantage. A class of drugs called PARP inhibitors exploits this weakness. In healthy cells, a protein called PARP handles minor, everyday DNA damage. When a PARP inhibitor blocks that protein, cells must rely on the BRCA1 repair pathway instead. Normal cells can do this without a problem, but cancer cells with a broken BRCA1 gene cannot. They accumulate so much unrepaired DNA damage that they die.
This targeted approach has changed the treatment landscape for BRCA1-related breast and ovarian cancers. PARP inhibitors can be used alone or alongside chemotherapy, and they tend to cause fewer severe side effects than traditional chemotherapy because they selectively target cells that lack functional DNA repair. For many patients with BRCA1-mutated cancers, these drugs have extended survival and improved quality of life.
What a Positive Result Means for Your Family
If you test positive for a BRCA1 mutation, it has implications beyond your own health. Your siblings each had a 50 percent chance of inheriting the same mutation. Your children do too. Sharing your result with close relatives gives them the option to get tested and, if positive, to begin early screening that can catch cancer at its most treatable stage. Ovarian cancer in particular is difficult to detect without knowing you’re at risk, and early screening in carriers can be lifesaving.
A negative result in someone whose family carries a known BRCA1 mutation is genuinely reassuring. It means that person’s cancer risk returns to the general population level. But a negative result without a known family mutation is harder to interpret, since other genes and risk factors may still be at play. This is one reason genetic counseling is valuable before and after testing.