Fig. 5. (A-D) Telomeric metaphase singlets hybridize more intensely compared with the single components of a doublet signal. Combined FISH-IF utilizing a 17p telomeric probe and an antibody for H3P was performed on pre-senescent cells aged in culture (A,B) and presenescent fibroblasts from elderly people (C,D). The FISH signal is detected with FITC (green) and the H3P with Cy-3 (red). All four metaphase cells display one singlet signal and one doublet signal. The hybridization signal intensity of the singlet appears stronger than that of each of the two dots composing the doublet. Bar, 10 µm.