Genomic abnormalities resulting in loss of DNA repair function are associated with the development of several tumours, i.e. loss of BRCA1 or BRCA2 genes in hereditary ovarian or breast cancer [52]–[54], or defects in the DNA mismatch repair pathway in hereditary non-polyposis colorectal cancer [55]. This evidence concerns the gene BRCA1 and hereditary nonpolyposis colon cancer.