For example, breast cancer type 1 susceptibility protein (BRCA1) repairs DSBs by homologous recombination and is often mutated in breast and ovarian cancers.103 Loss of BRCA function allows premalignant cells to accumulate mutations and potentially transform into cancer cells. In order to maintain minimal genome integrity, these BRCA-deficient cancer cells rely more on the remaining intact DDR pathways, such as single-strand break (SSB) repair. This evidence concerns the gene BRCA1 and cancer.