Analysis of the derivative chromosome 19. (A) Partial GTG-banded karyogram showing a normal and a derivative chromosome 19 (left- and right-hand side, respectively). The arrow points to the additive band from 17q23. (B) Metaphase-FISH analysis using the E2A gene specific break-apart probe (green, D19S883; red, RH98588), which shows two normal fusion signals on both chromosomes. The arrow points to the additive chromosomal material on the derivative chromosome 19, which is illuminated by the DAPI counterstain.