Figure 1.

Schematic depiction of CHs, as known from cytogenetic diagnostics. Possible examples of centromeric amplification (A), centromeric diminution (B), pericentric inversion (C) and translocation (D) in chromosome 21 are shown, compared to a ‘normal’ chromosome 21 and a normal Y-chromosome (E). For clarity, the short arm of chromosome 21 is depicted in brown, the centromeric regions of chromosome 21 and Y-chromosome are in green and red, respectively, and the heterochromatic region of the Y-chromosome in the long arm is in blue. All aberrations shown do not cause any clinical problems.