BRCA1 and BRCA2 are the first two genes found to be associated with inherited forms of breast cancer. Both genes normally act as tumor suppressors, meaning that they help regulate cell division. When these genes are rendered inactive due to mutation, uncontrolled cell growth results, leading to breast cancer. Women with mutations in either gene have a much higher risk for developing breast cancer than women without mutations in the genes.
BRCA1 and BRCA2 are the names for two different genes that are associated with inherited or familial breast cancer. Everyone has two copies of these genes in all of their cells, and when they're unmutated, they serve to protect the cell against turning into a cancer cell. Some people are born with a specific mutation or different mutations in these genes, and these individuals are more susceptible to cancer. If they're a woman, they're at a greatly increased risk of having breast cancer in their lifetime. If they're a man, they may be at an increased risk of prostate cancer. People who inherit mutations have one copy of this gene that is not working. If, by chance, in some of their cells, either in their breast tissue or maybe their prostate tissue, the particular cell loses the other copy, that cell that has now lost both copies of BRCA1 or both copies of BRCA2 is unable to repair its DNA. And when it replicates its DNA during cell division, many, many more mistakes enter into that replicated DNA. Those mistakes make it more likely that cell will go on and start down the path to become a tumor.