Figure 1

Mapping of commercial probes. A: Partial karyotype of the infant with del(21)(q22) and supernumerary marker chromosome. B: fluorescence-in-situ-hybridization with probes for the Down-syndrome critical regions (B1: Kreatech, B2: Abbott) showing conflicting results. C: The array profile confirms the del(21)(q22) as well as the mosaicism for the derivative chromosome 21 and the supernumerary marker chromosome originating from chromosome 21.