A chimeric oncogene bcr/abl encoding activetyrosine kinase р210/р185 that participates in CML pathogenesis isformed in cells containing the Ph chromosome (Ph +  cells) due toreciprocal translocation of the 5’ fragment of the bcr geneand the 3’ fragment of the abl gene. This evidence concerns the gene ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive.