Chronic myeloid leukemia (CML) is characterized by the accumulation of myeloid precursors and mature myeloid cells and is driven by translocations between the BCR serine/threonine kinase gene and the ABL tyrosine kinase, resulting in a constitutively active ABL tyrosine kinase. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.