BRCA1 and ovarian cancer: We note that the level of carrier risk in UKB is lower than that reported by studies of BRCA1/2 penetrance in women who were selected for genetic testing on the basis of a family history of breast and/or ovarian cancer (e.g. [39]), which likely include a degree of residual ascertainment bias, but is broadly in line with estimates from other unselected population-based studies (e.g. [40–42]).