Summary of chromosome 21 abnormalities in 18 iAMP21 patients. (A) Heat map of chromosome 21 abnormalities detailing the regions of deletion (red), gain (green), and normal copy number (white) relative to genomic location. The CRA, as defined by sample 8983, is highlighted and R denotes that 4279 is a relapse sample. (B) Examples of chromosome 21 profiles from 3 iAMP21 patients clearly demonstrating the complexity and diversity of abnormalities targeting this chromosome. Sample 9864 has a single region of amplification and no telomeric deletion, sample 7583 has a characteristic stepwise profile with a telomeric deletion, and sample 8983 demonstrates a complex stepwise profile with interspersed regions of deletion. The CRA was defined by sample 8983, which is highlighted by a green bar. (C) Heat map showing the telomeric break points (indicated by a change from dark to light red) on chromosome 21 for the 18 patients profiled by aCGH. The region spans ∼ 9 mb, and the most centromeric and telomeric genes with break points, their relative location to the heat map, and the corresponding samples are shown. KCNJ6 is shown in black and PCNT in orange. Recurrent break points were identified in 4 genes: PDE9A (purple) and COL6A2 (blue) had identical break points, but the break points in DSCAM (green) and PCNT (orange) occurred at different genomic positions.