Loss-of-function mutations in breast cancer (BC) susceptibility genes 1 and 2 (BRCA1 and BRCA2) can result in homologous recombination deficiency (HRD), meaning that cells are reliant on lower-fidelity repair pathways, leading to accumulation of double-strand breaks, increased genomic instability and, potentially, tumourigenesis [1]. Here, BRCA1 is linked to breast cancer.