Biased chromosome fusions. (A-F) Anaphase bridges represent the involvement of the right arm of chromosome 2. Sequential FISH with telomere-adjacent 2R specific BAC clone revealed the fusion of 2R chromosome ends. The morphology of bridges is apparent from DAPI stained images (A, D). Using consecutively BAC F11L15 labelled with Cy3 (red, B and E) in the first FISH and labelled with SpectrumGreen (green, C and F), the direct contact of chromosome termini is highlighted. This respective alternation of signals during sequential FISH procedures was detected in the great majority of anaphase bridges tested in line K12. (A-C) Generation G3, (D-F) Generation G6.