 The TEL-AML1 fusion which results from the t(12;21) rearrangement in childhood B-precursor acute lymphoblastic leukaemia (B-precursor ALL) is often accompanied by loss of the untranslocated TEL allele.     ///    The TEL-AML1 fusion accompanied by loss of the untranslocated TEL allele in B-precursor acute lymphoblastic leukaemia of childhood..     ///    "This suggests that the initial or predisposing event is the generation of a TEL-AML1 fusion, followed by the promoting event of a deletion of a gene(s) on 12p. "    ///    was the substantial evolution of the primary clonal line containing the reciprocal TEL-AML1 fusion. 