BRCA2: A gene that normally acts to restrain the growth of cells in the breast and ovary but which, when mutated, may predispose to breast cancer and to ovarian cancer. BRCA2 mutations have also been discovered to be responsible for a significant fraction of early-onset prostate cancer. The first breast cancer genes identified were BRCA1 and BRCA2. Mutations of BRCA1 and BRCA2 account for about half of all cases of inherited breast cancer. These tumors tend to occur in young women. BRCA1 and BRCA2 are usually not involved in breast cancer that is not hereditary.
BRCA2 may regulate the fidelity of cytokinesis, the process by which two daughter cells separate at the completion of cell division. BRCA2 deficiency causes delays in cytokinesis and an increase in the frequency of binucleate cells, a consequence of defective cytokinesis. This role of BRCA2 in daughter cell separation may help to explain why BRCA2 tumor cells often contain alterations in chromosome number (aneuploidy), as well as structurally aberrant chromosomes.