Fig 1. Fluorescence signals resulting from hybridization of ABL (in red) and ASS (in blue) probes hybridized to extended chromatin from normal cells at different stages (a, b, and c) of condensation.

Fig 2. Fluorescence signals from a Ph⁺ bone marrow metaphase hybridized with the triple-probe/three-color system; ABL (in red), BCR (in green), and ASS (in blue): yellow arrows, Ph translocation t(9; 22)(q34.1; q11.2); white arrows, normal 9 and 22 homologues.

Fig 3. Diagrammatic presentation of fluorescent signals obtained using conventional two-probe system (A, B, and C) or triple-probe/three-color system (a, b, and c) hybridized to interphase cells: red, ABL; green, BCR; blue, ASS. The figure shows the signal patterns obtained from normal cells (A and a), BCR-ABL⁺ cells (B and b), and as a consequence of coincidental colocalization of BCR and ABL in normal cells (C and c).

Fig 4. Representative examples of the triple-probe/three-color system hybridized to interphase cells: red, ABL; blue, ASS; green, BCR. (a) Normal cells displaying two isolated green signals (BCR gene) marking the normal 22s and two colocalized red and blue (or purple) signals (ASS and ABL genes) from the normal 9s. (b) Ph⁺ cells displaying a typical colocalized red/green (or yellow) (BCR-ABL fusion gene) marking the Ph chromosome together with a single blue signal (ASS gene) from the derivative 9 chromosome with blue/red and isolated green signals from the normal 9 and 22 homologues. (c) Cells displaying a cluster of red/blue/green signals (arrow) marking coincidental colocalization of either ASS/ABL and BCR (false-positive) or BCR/ABL and ASS (false-negative). Note that cells displaying this signal pattern have not been scored. (d) A cell displaying a typical Ph⁺ signal pattern but without fusion of the BCR and ABL signals. Note that cells displaying this signal pattern have not been scored. (e) Cell displaying less than 6 signals have not been scored.