BRCA1 and BRCA1 are a human gene and its protein product, respectively. BRCA1 is a human tumor suppressor gene (to be specific, a caretaker gene), found in all humans; its protein, also called by the synonym breast cancer type 1 susceptibility protein, is responsible for repairing DNA.
BRCA1 and BRCA2 are normally expressed in the cells of breast and other tissue, where they help repair damaged DNA. They are involved in the repair of chromosomal damage with an important role in the error-free repair of DNA double-strand breaks. Although the terms “breast cancer susceptibility gene” and “breast cancer susceptibility protein” (used frequently both in and outside the medical literature) sound as if they describe an oncogene, BRCA1 and BRCA2 are normal; it is their mutation that is abnormal.

The human BRCA1 gene is located on the long (q) arm of chromosome 17 at region 2 band 1, from base pair 41,196,312 to base pair 41,277,500 (Build GRCh37/hg19) (map). BRCA1 orthologs have been identified in most mammals for which complete genome data are available.