Clonality of leukemias that developed in MSCV-FL mice. Southern blot analysis of EcoRI-digested genomic DNA (10 μg) from hematopoietic tissues of affected primary MSCV-FL recipients 196, 199, 203, and 204 with a neo probe. Abbreviations: BM, bone marrow; LN, lymph node; PB, peripheral blood mononuclear cells; SPL, spleen; THY, thymus. BALB/c SPL, negative control. The sizes (in kilobases) ofHindIII-digested λ phage DNA are indicated on the left of each panel.