Chronic Myeloid Leukemia (CML) is a myeloproliferative neoplasm caused by a reciprocal translocation between the Abelson murine leukemia (ABL1) gene on chromosome 9 and the breakpoint cluster region (BCR) on chromosome 221. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.