Southern blot analysis of DNA from the patient at first diagnosis (F) and at relapse phase (R) carrying the additional (5; 14)(q33; q32) translocation. Genomic DNA samples (5 μg each) were digested with Nco I, PvuII, and HindIII. Hybridization with probe Patients, a DNA fragment from PDGFRβ, shows DNA rearrangements in relapse phase. One rearranged band was detected upon Nco I and HindIII digestion and two rearranged bands were observed after PvuII digestion. The sizes of HindIII digested λ DNA markers are shown on the left of the panel.