Fig. 1

a Scheme of the probe design to detect deletions, duplications or inversions in the parents of an index patient with submicroscopic deletions or duplications. Abbreviations: CRP = critical region probe; Mb = megabasepair. b Schematic depiction of expected results. c-f Examples of parents of the index patients cases 18, 23, 32 and 54. The corresponding array-CGH results of the index patients are given in the figures; for the applied locus-specific probes see Additional file 1: Table S1. In Figs. c and d only the probe for the critical regions are depicted. Aberrant chromosomes are highlighted by arrowheads. c Case 18 had paternally derived deletion, as clearly visible. d Case 23 had a maternally derived duplication; the size of the duplication is too small to lead to two separated signals on the derivative chromosome 3, however, the signal-size and –intensity is clearly doubled compared to signal on the homologous. e A cryptic maternal inversion is depicted for case 32, as visible by the shift of the signal of the critical region probe. f No alterations could be detected in the parents of case 54; thus a ‘de novo’ formation of the copy number variant (CNV) in the index patient is suggested; as outlined in the text ‘de novo’ stands here for real de novo cases and such which may be based other (smaller) cryptic rearrangements not detectable by the here applied probe set