Fig 4a shows the cumulative incidence of breast cancer by BRCA1 status. The well-known importance of this genetic trait is reflected in the markedly higher cumulative incidence and age-specific incidence. Based on our models, as shown in Fig 4b, the differential in incidence reaches its peak around the age of 60, with much less when overall incidence declines with ages. The gene discussed is BRCA1; the disease is breast cancer.