BRCA 1 and 2 are breast cancer susceptibility proteins that play a role in DNA damage, repair, cell cycle progression, transcription and apoptosis, etc. The BRCA1 gene is expressed in numerous tissues, including breast and ovary, and encodes a predicted protein of 1863 amino acids. BRCA2 has been shown to be required for localization of Rad51 to sites of DSBs (double stranded breaks) in DNA. Cells lacking BRCA1 and BRCA2 cannot repair DSBs throμgh the Rad51-dependent process.