Here we consider mutual exclusivity with deletion and downregulation events affecting the following six genes (as genes A): ATM, BRCA1, BRCA2, CDH1, PTEN and TP53. These are tumour-suppressor genes that are central to or regulate DNA-damage response (DDR) functions, that is, genes that play important roles in maintaining the genomic integrity of the cell and control cell proliferation [11]. The gene discussed is BRCA1; the disease is neoplasm.