Mutations in the PALB2 protein and BRCA2 gene strongly predispose to breast cancer. PALB2 is a newly identified protein. Very interestingly, a novel mutation in PALB2 was found in approximately 0.5% of French-Canadian women with early-onset breast cancer. Also of interest, defects in BRCA2 and PALB2 cause a defect in homologous recombination, an important process to repair DNA damage within the cell. We aim to understand how the DNA repair proteins affect the cell ability to repair DNA by homologous recombination and then use this knowledge to design new therapies to reduce the viability of cancer cells.