What Is BRCA1, and How Does It Function? BRCA1 is a gene. Pathogenic variants in BRCA1 are associated with an increased risk of several cancers, including breast cancer. The BRCA1 gene codes for the breast cancer type 1 susceptibility protein, which is part of a group of proteins involved in repairing double-strand DNA breaks through a process called homologous recombination. As cells continually grow and divide, they depend on accurate DNA repair to function properly. BRCA1