The large number of substrates for activated ATM includes proteins such as the structural maintenance of chromosome-1 (SMC1), NBS1, checkpoint kinase 2 (CHK2), tumor protein 53 (P53), breast cancer early onset-1 (BRCA1) and mediator of DNA damage checkpoint protein-1 (MDC1) [25]. The gene discussed is BRCA1; the disease is breast carcinoma.