Few genes are as widely recognized as BRCA1 and BRCA2. But public awareness of these genes often outpaces understanding of what they actually do — and what a positive test result actually means.

What BRCA1 and BRCA2 Do

Despite their association with cancer, BRCA1 and BRCA2 are not cancer-causing genes. They are tumor suppressor genes — their normal function is to help prevent cancer.

Both genes encode proteins that play critical roles in DNA repair, specifically in a pathway called homologous recombination repair (HRR). When DNA sustains double-strand breaks — one of the most serious types of DNA damage — the BRCA1 and BRCA2 proteins help coordinate the repair process.

When these proteins are working normally, damaged DNA is repaired accurately. When they are absent or non-functional, double-strand breaks are repaired by less accurate backup pathways, which can introduce errors. Over time, these errors can accumulate and contribute to cancer development.

What a Pathogenic Variant Means

A pathogenic variant in BRCA1 or BRCA2 means one copy of the gene carries a change that disrupts the protein's function.

Because most people have two copies of each gene, one functional copy is usually enough to maintain DNA repair. This is why BRCA1 and BRCA2 follow an autosomal dominant inheritance pattern for cancer risk — one inherited non-functional copy is enough to substantially raise risk — but the cancer itself typically requires loss of the second copy in a specific cell.

Cancer Risks Associated With BRCA Variants

The cancer risks associated with BRCA1 and BRCA2 pathogenic variants are substantially elevated compared to the general population, but they are not certainties.

BRCA1 pathogenic variants are associated with:

• Lifetime breast cancer risk: approximately 50–72%
• Lifetime ovarian cancer risk: approximately 44–46%
• Elevated risk of pancreatic cancer

BRCA2 pathogenic variants are associated with:

• Lifetime breast cancer risk: approximately 45–69%
• Lifetime ovarian cancer risk: approximately 11–17%
• Elevated risk of pancreatic cancer
• Elevated risk of prostate cancer (particularly aggressive forms)
• Elevated risk of male breast cancer

These figures are population-level estimates from large studies. Individual risk depends on additional factors including family history, other genetic variants, and lifestyle.

What a Positive Result Does Not Mean

A positive BRCA1 or BRCA2 result does not mean cancer is present or inevitable. Many people with pathogenic variants in these genes never develop cancer.

It does mean that the risk is substantially elevated compared to the general population, and that surveillance and prevention strategies — including enhanced screening, risk-reducing medications, or risk-reducing surgery — are worth discussing with a specialist.

Implications for Family Members

Because BRCA1 and BRCA2 variants follow autosomal dominant inheritance, each first-degree relative of someone with a pathogenic variant has a 50% chance of having inherited the same variant. Cascade testing — offering genetic testing to relatives — is an important part of managing hereditary cancer risk.

At Genetic Insights, we help patients understand their results in full context and discuss what those results mean for their family.

Key Takeaway: BRCA1 and BRCA2 are DNA repair genes. Pathogenic variants substantially raise cancer risk but do not make cancer certain. A positive result opens the door to surveillance and prevention — not a diagnosis.

Sources: NCCN Genetic/Familial High-Risk Assessment: Breast, Ovarian, and Pancreatic; NCI BRCA Fact Sheet