The Breast Cancer 1 and 2 genes, which are the two major genes responsible for inherited predisposition to breast cancer (and, especially for BRCA1, to ovarian cancer as well). These genes are responsible for 80% to 90% of hereditary breast cancer. BRCA1 was discovered in 1994 and BRCA2 was discovered in 1995.
First breast cancer genes to be identified. Mutated forms of these genes are believed to be responsible for about one-half the cases of inherited breast cancer, especially those that occur in younger women, and also to increase a woman's risk for ovarian cancer. Both are tumor-suppressor genes.
These are two genes that are known to play a part in breast cancer risk. Women who inherit a defective BRCA1 or BRCA2 gene from either or both of their parents may have a higher chance of developing breast cancer than women who have not inherited one of these defective genes. Women who have a high rate of breast cancer in their families can have a test done that can tell them if they have a defective BRCA1 or BRCA2 gene.