Like many other tumor suppressor genes, BRCA1 regulates the cycle of cell division by keeping cells from growing and dividing too rapidly or in an uncontrolled way.

In particular, it inhibits the growth of cells that line the milk ducts in the breast.

The protein made by the BRCA1 gene is directly involved in the repair of damaged DNA.

In the nucleus of many types of normal cells, the BRCA1 protein interacts with the protein produced by the RAD51 gene to mend breaks in DNA.