1, 3 and 4). These changes were identified mostly in progenitors and HSC/MPP. The RT-qPCR revealed no TEL/AML1 fusion transcripts in tested subpopulations of healthy probands. Results from ALL patients, regardless of their genetic examination at the time of diagnosis and presence of PFG, were compared to data obtained from healthy children (Fig. 2). For statistical analysis, we pooled our FISH data with the results of another three healthy probands tested for the presence of BCR-ABL by the same method in our previous study19. The gene discussed is ABL1; the disease is acute lymphoblastic leukemia.