cancer gene definition
BRCA1: A gene that normally acts to restrain the growth of cells in the breast but which, when mutated, predisposes to breast cancer. The gene's full name is breast cancer 1, early onset.The BRCA1 gene belongs to a class of genes known as tumor suppressor genes.n addition to breast cancer, mutations in the BRCA1 gene also increase the risk of ovarian cancer, prostate cancer, and colon cancer. The BRCA1 gene is located on chromosome 17q21 -- the long (q) arm of chromosome 17 at position 21.