Figure 13.22 The formation of the bcr-abl gene by translocation. In chronic myelogenous leukemia, parts of chromosomes 9 and 22 are reciprocally exchanged, causing the bcr and abl genes to fuse. The protein kinase encoded by the bcr-abl gene is expressed at higher levels in cells having this translocation than is that encoded by the c-abl gene in normal cells.