The Philadelphia (Ph) chromosome, created by a translocation between chromosomes 9 and 22, generates the Breakpoint Cluster Region-Abelson leukemia virus (BCR-ABL), which leads to the abnormal protein BCR-ABL1 tyrosine kinase, central to the development of CML [3]. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.