Figure 2.

Identification of rearrangements within the MLL bcr by Southern blot in leukemias of infant twins 68 and 72 and in peripheral blood mononuclear cells (PBMCs) of twin 72 7 weeks before the onset of clinical leukemia. Intensity of identical rearrangements in preleukemic PBMCs of twin 72 relative to the germ-line band suggests that the translocation was not constitutional. BamHI-digested DNAs were hybridized with B859 human MLL cDNA probe spanning exons 5–11 (13). The 8.3-kb fragment is from the unrearranged allele (dash marks). Control DNA from PBMCs of a normal individual shows the germ-line pattern. Arrows show rearrangements.