BamHI restriction map of CBFA2 on chromosome 21 in the region containing the breakpoints of the t(8;21), t(3;21) and newly identified translocations involving CBFA2(vertical arrows). The breakpoint region for the t(12;21)(p13;q22) associated with childhood B-cell ALL is located 5′ of the map area. The numbered vertical bars above the line represent exons and the vertical lines below the line indicate BamHI sites. The direction of transcription is indicated by a horizontal arrow. The recombinant phage walking clones 13′ through wc-10 are indicated by horizontal lines below the map. wc-10 was not precisely mapped and is indicated by a dashed line. Genomic regions indicated by a dashed line have not been precisely mapped.