In this pedigree, it again becomes clear that most mutations in cancer susceptibility genes are germline and pass as dominant traits with incomplete penetrance. Note the female carrier who lives to age 83 and dies of natural causes even though her mother was affected by breast cancer and died at age 48. Also note two males: one diagnosed with breast cancer and the other with prostate cancer. Men who inherit an abnormal BRCA2 gene have an increased risk (80 times the lifetime risk of men without the mutation) for male breast cancer. They also are three to seven times more likely than men without the mutation to develop prostate cancer.

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