Duplication architecture in 17q21-23. Structure of duplication regions: large (≥10 kb), high identity (≥95%) segmental duplications are shown between DUPA, DUPA', DUPB and DUPB' (green-striped blocks in the first row) as pairwise alignments (blue lines). Underlying duplicon mosaic structure (second bottom row) was defined using the program DupMasker . The different colors represent the different cytoband locations for the ancestral loci of duplications (see the color key code below; NA, ancestral locus not determined) . DUPA-DUPB' share fewer high-identity duplications compared to DUPA-DUPB (total aligned = 104.7 kb, average identity = 97.4%; Additional data file 6). The PBR and DBR are shown as red-striped blocks (third row). The proximal and distal breakpoint regions found in microdeletion cases (PBR' and DRB', fourth row), according to Mefford et al. , are shown as orange-striped blocks.