brca1 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.any are associated with an increased risk of cancer. These mutations can be changes in one or a small number of DNA base pairs, or, in some cases, large rearrangements of DNA. A mutated BRCA1 gene usually makes a protein that does not function properly because it is abnormally short.