Breast cancer type 1 susceptibility protein (BRCA1) plays a central role in DNA repair by facilitating cellular response to DNA repair. BRCA1 is required for appropriate cell cycle arrests after ionizing irradiation in both the S-phase and the G2 phase of the cell cycle. BRCA1 is part of the BRCA1-associated genome surveillance comple, Xenopus/Amphibian, (BASC), which contains BRCA1,Mouse,SH2,Mouse,SH6,Mouse,LH1, ATM, BLM,PorcineMS2 and the RAD50-MRE11-NBS1 protein comple, Xenopus/Amphibian,. Defects in BRCA1 are a cause of genetic susceptibility to breast and ovarian cancers.