FISH analysis of UPN 17 using the TEL/AML1 dual-color, dual-fusion translocation probe. Three RUNX1/AML1 signals are observed in red, on 2 normal chromosomes 21 and on the derivative chromosome 1. The residual signal RUNX1/AML1 on the derivative chromosome 21 is lost. The green signal corresponds to the TEL locus 12p12 and the loss of the second green signal confirms the del(12)(p11;p13) observed on karyotyping analysis. Image was acquired with a Leica DMXRA microscope (Leica, Wetzlar, Germany) fitted with a 100×/1.30 numeric aperture oil objective, a Photometrics Sensys CCD camera (Roper Scientific, Tucson, AZ) and QFISH image acquisition software (Leica).