This variant of BRCA1 has the following properties: (a) it is highly expressed in some mammary cell lines [34], (b) it contains the conserved N-terminal RING E3 ligase domain and C-terminal BRCT repeats critical for BRCA1 function in DNA repair and breast cancer suppression [35] and (c) is able to rescue the otherwise deleterious deletion of BRCA1 during mouse development [36]. The gene discussed is BRCA1; the disease is breast cancer.