The presence of fusion oncogene BCR-ABL1 and generating a 210 KD chimeric oncoprotein (P210) with the constitutive activity of tyrosine kinase leads to clonal expansion of hematopoietic stem cell (HSC) and the pathogenesis of CML [3]. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.