During this event, two genes, Abelson 1 (ABL1), located on chromosome 9, and the Breakpoint Cluster Region (BCR), on chromosome 22, generate a fusion gene called BCR-ABL1, that, along with the Philadelphia chromosome, is the main diagnostic marker of CML (1). This evidence concerns the gene BCR and chronic myelogenous leukemia, BCR-ABL1 positive.