Molecular studies revealed MLL rearrangement by both fluorescence in situ hybridization and Southern blot analysis, and MLL/AF1q, but not the reciprocal message (i.e., AF1q/MLL), was amplified by polymerase chain reaction.     ///    Sequence analysis of MLL/AF1q revealed an in-frame fusion between MLL exon 6 and the breakpoint located six bases upstream of the ATG start site for AF1q. 