Everyone's genetic code is made up of 3 billion letters - a Cs, Gs, Ts or As.
All those codes contain mistakes. Most of them are harmless, but what these researchers have done is to look for the ones that aren't.
Scientists did that by cracking the codes of 100,000 people with either breast cancer, prostate cancer or ovarian cancer.
They found 80 of those mistakes that put people at high risk of getting cancer.
They say that a test for those mistakes could be available in GPs surgeries soon.
If you find out you've got one of those genetic alterations, it doesn't mean you will get cancer, just that you are at high risk. But that might convince you to, for example, cut down on drinking or smoking or to go for more regular screenings.