BRCA1 is a human tumor suppressor gene (also known as a caretaker gene) and is responsible for repairing DNA. BRCA1 and BRCA2 are unrelated proteins, but both are normally expressed in the cells of breast and other tissue, where they help repair damaged DNA, or destroy cells if DNA cannot be repaired via apoptosis ( controlled cell death) which stops the replication of a damaged cell. The greatest risk factor for breast and ovarian cancer is inheritance of a mutation in one of the breast cancer susceptibility genes, BRCA1 or BRCA2. This is a predisposition and not a predetermination.
PARP is a protein found in our cells, it stands for poly-ADP ribose polymerase. It helps damaged cells to repair themselves. As a cancer treatment, PARP inhibitors stop the PARP from doing its repair work in cancer cells and the cell dies rather than replicating and becoming a tumor. Poly(ADP-ribose) polymerase (PARP) is a nuclear enzyme that signals the presence of DNA damage by catalyzing the addition of ADP-ribose units to DNA, histones, and other DNA repair enzymes by facilitating repair of DNA strand breaks. Poly(ADP-ribose) polymerases (PARPs) play an important role in base excision repair pathway in the setting of single-strand DNA breaks.
Read More about Many other Genes and Genetic Transcriptions Involved in DNA Repair