ABSTRACT
INTRODUCTION The Philadelphia (Ph) chromosome is an acquired cytogenetic abnormality present in all leukemic cells of the myeloid lineage and in some B cells and T cells in patients with CML. It is formed as a result of a reciprocal translocation of genetic material of chromosomes 9 and 22 (Figs. 1.1 and 3.1). This balanced translocation results in a BCR-ABL1 fusion gene on the Ph chromosome and also a “reciprocal” fusion gene, designated ABL-BCR, on the derivative 9q chromosome (der 9q+).
