The short answer
If either parent has a confirmed harmful change in BRCA1 or BRCA2, each of their children has a 50% chance of inheriting it. The chance is the same for sons and daughters, and it starts again with every child. Inheriting it means a higher risk of certain cancers — not a certainty that you will get cancer. A negative test for the exact change your family carries usually means you did not inherit that risk, and cannot pass it on.
Five steps, in this order
- Get a copy of your parent’s laboratory report. The gene name on its own is not enough — you need the exact change and how the laboratory classified it.
- Check that it is an inherited result. A BRCA change found only in a tumour is not automatically something that was present from birth.
- Ask for a test for that exact family change. This is far clearer than starting with a broad panel or a home kit.
- Treat positive, negative and uncertain results differently. A VUS is not the same thing as a harmful BRCA change.
- Make the medical plan after the result, not before it. Screening and prevention depend on the gene, your age, your sex and your own history.
That order avoids the two commonest dead ends: testing for the wrong changes, and treating an uncertain result as a diagnosis.
Why the answer is one in two
Everyone has two copies of BRCA1 and two of BRCA2 — one from each parent. A parent with a harmful change has it in one copy, with a working copy alongside it. Each child gets one of the two, at random.
That is a dominant pattern:
- a 50% chance of inheriting the harmful copy;
- a 50% chance of inheriting the working one;
- the same chance for sons and daughters;
- a fresh 50/50 in every pregnancy.
Three brothers and sisters can all inherit it, none can, or anything in between. What happened to an older sibling tells you nothing about your own chance.
You inherit a risk, not cancer
BRCA genes help repair damaged DNA. An inherited change makes it easier for cells to accumulate further damage over a lifetime, which is what can eventually lead to cancer. Nobody is born with cancer because of it, and not everyone who inherits it develops cancer.
The cancers most strongly linked to BRCA changes are breast and ovarian cancer. BRCA2 in particular can also raise the risk of male breast cancer and prostate cancer, and both genes can be relevant to pancreatic cancer. The risks are not the same for BRCA1 and BRCA2, or for every family.
So the sentence “I have a 50% chance” should always finish with of carrying the family’s gene change. Your chance of actually developing a particular cancer is a different number.
Your father’s side counts just as much
A common and costly mistake is to think of BRCA as something that travels through women. It does not. A man can carry a BRCA change, has cancer risks of his own because of it, and passes it to half his children on average.
When you write the family history down, include both sides — and look beyond breast cancer. Ovarian, pancreatic, prostate and male breast cancer on your father’s side are all relevant.
The best test is the family’s own test
If your parent’s report names a specific harmful change, your test can look for exactly that. The result is then clean:
| Your result | What it usually means |
|---|---|
| Positive | You inherited it, and can discuss screening and risk-reducing options |
| Negative for the family change | You did not inherit that family risk, and cannot pass it on |
| Unclear | The report needs review before anyone draws a conclusion |
If nobody in the family who has had cancer has ever had useful genetic testing, a negative result in a healthy person is much harder to interpret. It may mean there is no inherited cause — or that the test did not cover it.
Tumour tests and home kits are not the same thing
A BRCA change found in a tumour sample may exist only in the cancer cells. It might also be inherited, but a separate blood or saliva test is needed to find out. A tumour report on its own does not put a child’s chance at 50%.
Many home tests look for only a handful of specific BRCA changes, common in particular populations. A negative can easily miss your family’s change. The document that is actually useful is the laboratory report from the affected relative.
What happens after a positive result
A positive result can change when and how you are screened, and opens a discussion about medication or risk-reducing surgery. The right plan depends on the gene, your age, your sex, your medical history and what you want.
It also gives your relatives something definite to test for. Your brothers and sisters have the same 50% starting chance. Each of your own children would have a 50% chance if you test positive — and no chance of inheriting that particular change if you test negative.
Common questions
- Is it still 50% if it is my father who has the BRCA mutation?
- Yes. BRCA1 and BRCA2 are not on the sex chromosomes. Fathers and mothers pass them on equally, to sons and daughters alike.
- Does a positive BRCA test mean I will get cancer?
- No. It means your risk is higher than average. How much higher depends on the gene, the type of cancer, your age, your sex and your family history.
- Who in the family should be tested first?
- Usually the relative who has had a relevant cancer. Finding the cause in them turns everyone else's test into a search for one known change, which is far quicker and far clearer.
- My parent's result says VUS. What does that mean?
- A "variant of uncertain significance" is a change the laboratory could not classify as harmful or harmless. It is not a BRCA diagnosis, and relatives are not usually tested for it to make medical decisions unless it is later reclassified.
- Can a home DNA kit tell me?
- Not reliably. Most consumer kits check only a small number of specific BRCA changes, so a negative result can easily miss your family's one. Ask for a clinical test for the exact change on your parent's report.