BRCA1 and breast cancer: Unlike GWAS studies that are based on common variants, this study pursued the goal to predict BRCA1 penetrance and AAO of breast cancer by analysing rare variants in genes that are part of the DNA damage response and genome integrity maintenance pathways as well as genes which are interacting with BRCA1. Accurate prediction of AAO can become of clinical relevance in order to prevent overtreatment of carriers who will never develop breast cancer during their lifetime or may develop it later in life.