BRCA1 and BRCA2: What These Genes Actually Do and Why They Matter

By Amanda Shrewsbury, MS, CGC

BRCA1 and BRCA2 are probably the most recognized gene names in all of medicine. Most people have heard of them. Far fewer actually understand what they do, what it means to carry a variant in one of them, or who should consider getting tested.

If you've been wondering whether BRCA is something you should think about for yourself or your family, this post will walk you through the basics: what these genes are, what happens when they don't work properly, what the actual cancer risks look like, and what you can do about it. Whether you're exploring your family history, were recently diagnosed with cancer and told to consider genetic testing, or are supporting a family member through that process, this information is for you.

What Are BRCA1 and BRCA2?

Every person has two copies of both the BRCA1 gene and the BRCA2 gene. You inherit one copy of each from your mother and one from your father. The name BRCA stands for BReast CAncer gene, but that name can be a little misleading, because these genes aren't just about breast cancer, and having them doesn't mean you have cancer.

In fact, BRCA1 and BRCA2 are tumor suppressor genes. Their normal job is to protect you. They produce proteins that help repair damaged DNA inside your cells. Every day, your cells accumulate small amounts of DNA damage from normal processes like cell division, and BRCA1/2 proteins are part of the repair crew that fixes that damage before it can lead to uncontrolled cell growth.

When both copies of one of these genes are working properly, the repair system functions as it should. But when a person inherits a pathogenic variant (a change in the gene's DNA sequence that prevents it from working correctly) in one copy, their cells have a reduced ability to repair DNA damage. Over a lifetime, this increases the chance that enough damage accumulates to trigger cancer.

This is an important distinction: carrying a BRCA variant does not mean you will get cancer. It means your risk is elevated compared to the general population, and how much it's elevated depends on which gene is involved, your personal history, and other factors. And if you've already been diagnosed with cancer, a BRCA finding doesn't define your outcome. It gives your medical team more precise information to guide your treatment and helps identify which family members may benefit from testing.

What Are the Cancer Risks?

The most well-studied risks associated with BRCA1 and BRCA2 pathogenic variants are for breast and ovarian cancer, but these genes affect more than just those two cancer types.

For women with a BRCA1 pathogenic variant:

Breast cancer: approximately 55–72% lifetime risk (compared to about 13% in the general population)
Ovarian cancer (including fallopian tube and primary peritoneal cancer): approximately 39–58% lifetime risk (compared to about 1.1% in the general population)

For women with a BRCA2 pathogenic variant:

Breast cancer: approximately 45–69% lifetime risk
Ovarian cancer: approximately 13–29% lifetime risk

For men:

BRCA2 is associated with an increased risk of breast cancer (approximately 1.8–7% by age 70, compared to 0.1% in the general population), prostate cancer (particularly aggressive forms), and pancreatic cancer
BRCA1 may also be associated with an increase in prostate cancer risk, though the evidence is less conclusive than for BRCA2

Both BRCA1 and BRCA2 are associated with elevated risk for pancreatic cancer and, based on more recent research, potentially stomach cancer as well (National Cancer Institute, 2024; Li et al., 2022).

A few things worth emphasizing about these numbers. First, they are lifetime risks, meaning they represent the cumulative probability over an entire lifespan. They do not mean you have a 60% chance of getting cancer next year. Second, these risks are averages across populations of carriers. Your individual risk may be higher or lower depending on your family history, the specific location of the variant within the gene, and other genetic and lifestyle factors. A genetic counselor can help you understand what the numbers mean for you specifically.

How Are BRCA Variants Inherited?

BRCA1 and BRCA2 pathogenic variants follow an autosomal dominant inheritance pattern. In plain language, that means:

You only need one altered copy (from either parent) to have an increased cancer risk
If a parent carries a BRCA variant, each of their children has a 50% chance of inheriting it
The variant can be passed down by mothers or fathers equally. This is one of the most common misconceptions. Many people assume BRCA is only relevant on the mother's side. That's not true. A father who carries a BRCA2 variant, for example, can pass it to his daughter, who then has a significantly elevated breast and ovarian cancer risk, even though the father himself may never have developed cancer.

This is also why family history on both sides matters when assessing BRCA risk. A pattern of cancer on your father's side is just as relevant as on your mother's side.

Who Should Consider BRCA Testing?

Not everyone needs BRCA testing, but more people qualify than realize it. The National Comprehensive Cancer Network (NCCN) publishes clinical guidelines that outline who should be offered genetic testing. Some of the key indicators include:

Breast cancer diagnosed before age 50
Ovarian, fallopian tube, or primary peritoneal cancer at any age
Triple-negative breast cancer diagnosed at any age
Male breast cancer at any age
Pancreatic cancer, especially with a family history of BRCA-associated cancers
Metastatic or high-grade prostate cancer
Two or more close relatives on the same side of the family with breast, ovarian, pancreatic, or aggressive prostate cancer
A known BRCA pathogenic variant already identified in the family
Ashkenazi Jewish ancestry (BRCA founder variants are more common in this population, occurring in approximately 1 in 40 individuals compared to roughly 1 in 300–500 in the general population)

These criteria apply whether you have had cancer or not. If your family history includes any of the patterns above, genetic counseling can help determine whether testing is appropriate for you.

It's also worth knowing that guidelines don't capture every situation. Some families carry BRCA variants without meeting any of the traditional criteria, particularly in families that are small, have limited cancer history information, or have a high proportion of male relatives (who are less likely to develop BRCA-associated cancers and may mask the pattern). If something about your family history concerns you, a genetic counselor can help you think through it even if the "textbook" criteria don't apply.

What Happens If You Test Positive?

A positive BRCA result is significant, but it's not a verdict. It's information that opens up options, whether you're navigating a current cancer diagnosis or learning about your risk before cancer has developed. Depending on which gene is involved and your personal circumstances, your genetic counselor and medical team may discuss:

If you have not been diagnosed with cancer:

Enhanced screening:

Breast MRI screening starting at age 25, with mammography typically added around age 30, alternating every 6 months
Clinical breast exams every 6–12 months
For men with BRCA2, prostate cancer screening starting at age 40
Consideration of pancreatic cancer screening in families with a history of pancreatic cancer

Risk-reducing medications:

Medications like tamoxifen or aromatase inhibitors may reduce breast cancer risk in some carriers, particularly those with BRCA2 variants, which are more commonly associated with hormone-receptor-positive breast cancers

Risk-reducing surgery:

Prophylactic mastectomy (preventive removal of breast tissue) reduces breast cancer risk by approximately 90% or more
Prophylactic salpingo-oophorectomy (removal of the ovaries and fallopian tubes) is recommended for BRCA1 carriers typically between ages 35–40 and for BRCA2 carriers between ages 40–45. This significantly reduces ovarian cancer risk and, when performed before natural menopause, also provides some reduction in breast cancer risk

If you have been diagnosed with cancer:

Treatment guidance:

Your BRCA status can directly influence treatment decisions. Knowing you carry a BRCA variant helps your oncologist choose therapies that are more likely to be effective for your specific tumor biology.
PARP inhibitors are a class of drugs specifically designed to target cancers in people with BRCA variants, and they have shown significant benefit in treating BRCA-associated breast, ovarian, pancreatic, and prostate cancers, particularly in advanced or metastatic settings.
Your BRCA result may also inform surgical decisions, including whether to consider contralateral prophylactic mastectomy (removal of the unaffected breast) to reduce your elevated risk of developing a new cancer in the opposite breast.

Future cancer prevention:

Even after a cancer diagnosis, your BRCA status helps guide screening and prevention strategies for other BRCA-associated cancer types you may be at risk for going forward.

For everyone who tests positive:

Cascade testing for your family:

Once a BRCA variant is identified, close relatives can pursue cascade testing, which looks specifically for the known family variant. This gives a clear yes-or-no answer and is typically covered by insurance. Your counselor will provide a family letter you can share with relatives explaining what was found and what steps they may want to consider.

None of these decisions need to be made immediately after receiving your result. Your genetic counselor will walk you through each option, and together with your medical team, you'll build a plan that fits your values, your risk level, and your life.

What Does a Negative BRCA Result Mean?

A negative BRCA result means that testing did not find a pathogenic variant in the genes that were analyzed. What that means in practice depends on context:

If a known variant exists in your family and you tested negative for it, you very likely did not inherit the elevated risk associated with that variant. Your cancer screening recommendations would generally return to those for the general population.
If no one in your family has been tested before, a negative result is less conclusive. It's possible that a hereditary risk exists in a gene that wasn't included on the panel, or that there's a variant the test couldn't detect. This is sometimes called an "uninformative negative" result. Your counselor will explain what additional screening may still be appropriate based on your family history.

How Common Are BRCA Variants?

About 1 in 300 to 1 in 500 people in the general population carry a BRCA1 or BRCA2 pathogenic variant. In certain populations, the frequency is higher. In people of Ashkenazi Jewish descent, approximately 1 in 40 individuals carries one of three specific BRCA founder variants (National Cancer Institute, 2024).

Because carriers don't always develop cancer, and because the family history pattern can be masked by small families, male-predominant lineages, or incomplete information, many people carry BRCA variants without ever knowing it. This is exactly why genetic counseling and testing exist: to find these variants before cancer develops, when there's still time to act on the information.

Are There Other Cancer Risk Genes Beyond BRCA?

BRCA1 and BRCA2 get the most attention, but they are not the only genes associated with inherited risk for breast, ovarian, colorectal, endometrial, pancreatic, prostate, and other cancers. There are dozens of other genes that, when altered, can increase the likelihood of developing these and other cancer types. Some of the most well-established include:

PALB2 — associated with a significantly elevated risk of breast cancer, and also linked to pancreatic cancer, with growing evidence of a moderately increased ovarian cancer risk. PALB2 works closely with BRCA2 in the DNA repair process, and risk estimates for breast cancer in PALB2 carriers can approach those of BRCA2, particularly in carriers with a strong family history of breast cancer.
Lynch syndrome genes (MLH1, MSH2, MSH6, PMS2, EPCAM) — associated with substantially increased risks of colorectal and endometrial cancers, as well as elevated risk for ovarian, gastric, urinary tract, and other cancers.
TP53 — associated with Li-Fraumeni syndrome, a condition that carries a very high lifetime risk for multiple cancer types including breast cancer, sarcomas, brain tumors, and adrenocortical carcinoma, often at unusually young ages.
ATM, CHEK2, and others — associated with moderate increases in breast cancer risk and, in some cases, other cancer types. The clinical significance and management recommendations for these genes continue to evolve as more research becomes available.
RAD51C and RAD51D — primarily associated with increased ovarian cancer risk, with emerging evidence for breast cancer as well.

This is why most genetic counselors today recommend multigene panel testing rather than testing for BRCA1 and BRCA2 alone. A multigene panel analyzes many cancer-associated genes at once, which provides a more comprehensive picture of your inherited risk. If your family history suggests hereditary cancer but doesn't fit a classic BRCA pattern, variants in one of these other genes may explain the pattern.

Your genetic counselor will help determine which panel is most appropriate for your situation based on your personal and family history. Testing only for BRCA1 and BRCA2 when a broader panel is warranted could miss clinically important findings in other genes.

Knowledge Creates Options

A BRCA result can feel heavy at first. But what it really gives you is information that creates options. For those who haven't been diagnosed, it opens the door to screening that catches cancer earlier and interventions that can reduce risk substantially. For those who have, it can guide treatment and shape the path forward. And for families, it's the beginning of a conversation that can protect the people you love. People without this knowledge don't have those options. People with it do.

If your family history includes any of the patterns described in our family history guide, or if you've been wondering whether BRCA testing is right for you, a genetic counselor can help you sort through the question. Not sure what happens during an appointment? Read our walkthrough: What Actually Happens During a Genetic Counseling Appointment. Already have results? See What Your Genetic Test Results Actually Mean.

References

National Cancer Institute. (2024). BRCA gene changes: Cancer risk and genetic testing fact sheet. U.S. Department of Health and Human Services.
Li, S., Silvestri, V., Leslie, G., Rebbeck, T. R., Neuhausen, S. L., Hopper, J. L., et al. (2022). Cancer risks associated with BRCA1 and BRCA2 pathogenic variants. Journal of Clinical Oncology, 40(14), 1529–1541.
National Comprehensive Cancer Network. (2025). Genetic/familial high-risk assessment: Breast, ovarian, pancreatic, and prostate (Version 2.2025).
Kuchenbaecker, K. B., Hopper, J. L., Barnes, D. R., et al. (2017). Risks of breast, ovarian, and contralateral breast cancer for BRCA1 and BRCA2 mutation carriers. JAMA, 317(23), 2402–2416.