(A) Panhandle variant PCR products from der (11) chromosome of t(11;22)(q23;q11.2) in AMLs of infant twins 68 and 72. (B) Summary of t(11;22) breakpoint junction and partner DNA identified by directly sequencing panhandle variant PCR products from AML of patient 68 and sequencing products of panhandle variant PCR from leukemias of patients 68 and 72 subcloned by recombination PCR. Comparison with normal sequence identified the breakpoint at nucleotide 2,672 in MLL intron 7 (bold arrow). Primer 3 serves as the primer in the final PCR (see Fig. 1). The 5′ 2,622 bp include primer 3 and MLL bcr sequence to breakpoint at position 2,672 in intron 7. The 1,240 bp of 3′ sequence are partner DNA, and the most 3′ 31 bp of sequence are the complement of the ligated oligonucleotide (i.e., the complement of primer 3). Underlines show short segments of homology between MLL and hCDCrel at respective breakpoint junctions. Positions of relevant cosmid clones in chromosome band 22q11.2 deletion syndromes are shown at top (GenBank accession nos. AC000093 and AC000091). rc indicates that GenBank entry is reverse complement of hCDCrel.