BRCA1 and breast cancer: Similarly, introduction of patient‐relevant Brca1 mutations in a conditional mouse model of BRCA1‐associated breast cancer showed that, in contrast to Brca1‐null tumors, mammary tumors with expression of Brca1 alleles harboring mutations in the RING domain readily acquired resistance to DNA‐damaging drugs due to residual activity of the RING‐less BRCA1 protein (Drost et al, 2011, 2016).