In this pedigree of a family with a BRCA1 mutation, numbers below each person indicate age at first cancer diagnosis, if affected; age at death, if deceased; and age at interview, if alive. This family exemplifies several hallmarks of hereditary breast and ovarian cancer. The fact that the mutation is passed on by autosomal dominant transmission is evident in that approximately 50 percent of family members in each generation carry the mutation. Notice that an unaffected father passes the mutation to his affected daughter, showing that transmission of the BRCA1 mutation can occur through either parent. Note the high penetrance of the disease and early age at onset. The penetration is incomplete, though high, as shown by one female carrier who lives to age 86 and another who lives to age 92 without a diagnosis of breast or ovarian cancer.