This may be the case, for example, in the case of chronic myeloid leukemia where mutation rates are elevated by the BCR-ABL mutation or in colon carcinogenesis where somatic deletions in simple repeat sequences have been shown to increase mutation rates in these tumors (Ionov et al. 1993). This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.