Figure 3: Metaphases hybridized with Down-syndrome critical region probe LSI 21 (a) and whole chromosome paint (WCP) for chromosome 21 (b). (a) LSI showed 2 normal signals at the study locus 21q22.13-q22.2. (b) WCP 22 revealed a complete hybridization of the two long arms of chromosome 21. Neither der 22 nor other chromosomes revealed signal for any of the two probes