Distribution of senescence-related γ-foci in human fibroblasts. (A-B) Distribution of γ-foci on the metaphases of low and high population doublings (PDs) (pre-senescent), human embryo lung fibroblast (WI-38) (A) and foreskin fibroblast (BJ) (B). Proportion (%) of each type of damage is shown in each graph bar. Scoring is as in Figure 1B. (C-D) Scoring of the γ-foci as along the chromatid arms proximal to the telomere, along the chromatid arms distal to the telomeres, on the chromatid ends with fluorescence in situ hybridization (FISH) signal or on the chromatid ends without FISH signal. Low and high PDs of WI-38 cells (C) and BJ cells (D). On average more than 10 metaphases were screened per point in independent experiments. Error bars signify standard errors.