FISH analysis of the ETV6 rearrangement. FISH with the ETV6-containing YAC 964c10 to leukemic metaphases. Arrows indicate fluorescent signals corresponding to YAC 964c10 on the der(1) and the der(12); the arrowhead shows the normal chromosome 12 homologue. The G-banding on the chromosomes was obtained by inverting the DAPI-counterstained image.