The schematics representing human BRCA1 (1863 amino acids) and BRCA2 (3418 amino acids) are not to the same scale. Regions depicted as white boxes in BRCA1 include the N-terminal RING domain, the C-terminal tandem BRCT (tBRCT) domains, and a region predicted to encode coiled coil (CC) motifs. Regions depicted in BRCA2 include the conserved region of exon 11 encoding 8 repeats of the 30-40 amino acid BRC motif (white line), as well as the adjoining helical domain (HD, white box), and OB1-3 folds (white box), which together form a DNA-binding domain. The segments binding DSS1 (DSS1-b) and encoding the tower domain (TD) are represented as black lines. Proposed mutation cluster regions predisposing preferentially to breast (BCCR, green) or ovarian (OvCCR, red) are shown, based on data from Rebbeck et al., 2015. Caveats concerning the nature and mechanism of the proposed cluster regions are summarized in the main text.