The 8q24.13 breakpoint occurs at the center of a perfect 290-bp AT-rich palindromic sequence. (A) Junction fragment sequence obtained by nested primer PCR using genomic DNA from the balanced t(8;22) carrier (shown centromere to telomere). 8q24 sequence is shown in plain text while that from the recurrent 22q11.2 breakpoint is shown in blue. Underlined 8q24 sequence indicates the inverted repeat sequences flanking the 8q24 breakpoint. (B) Comparison of the 8q24 breakpoint deduced from junction fragments originating from the balanced t(8;22) carrier with “normal” AT-rich sequence present in genomic databases (genomic mapping contig, NT_008046). A 51-bp repeated sequence highlighted in red comprises a potential VNTR. Palindromic sequence at the deduced 8q24 breakpoint is underlined. (C) Potential ssDNA secondary structures formed at the 8q24 breakpoint region by sequence deduced from the t(8;22) carrier (top) and normal sequence (bottom) are depicted. The 8q24 breakpoint (red arrow) is located at the tip of an undisrupted 145 base pair stem–loop structure.
