BRCA1 and cancer: Because BRCA1 plays a critical role in DNA end resection and RAD51 loading, BRCA1-mutated cancers are unable to effectively carry out HR repair and rely on alternative pathways, such as non-homologous end joining (NHEJ), single-strand annealing (SSA) and microhomology-mediated end joining (MMEJ) (1,4,5).