In the early 1970′s, Drs. Janet Rowley, Peter Nowell and Alfred Knudson, studying leukemia cell chromosomes under the microscope, suggested that a specific chromosomal translocation that resulted in the formation of the BCR-ABL fusion oncogene caused chronic myelogenous leukemia (CML); this observation established a foundation for clinical cancer genomics [131]. The gene discussed is BCR; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.