Telomere PNA-FISH was used to detect chromosomal aberrations (CA) in metaphases. A-R. Cy3-telomere and FITC-centromere PNA probes, depicted by the red and green signals respectively, and DAPI (blue) counterstain were used. Cell type and H2O2 concentrations used on the cells are stated within the parentheses. A. Metaphase spread with 46 chromosomes and no detected aberrations (XPA-L, 20 μM). B-H. Aberrations categorized as breaks. Interstitial deletion resulting in a B. double minute (XPD-L, 0 μM) and C. acentric fragment (XPD-L, 0 μM). D. Terminal break in chromosome resulting in an acentric fragment with telomere signals (XPA-L, 60 μM). E. Interstitial deletion resulting in a centric fragment (XPA-L, 80 μM). F. Undetected telomere signals (XPB-L, 0 μM). G. Chromatid break (XPD-L, 80 μM). H. Chromosome break (Normal-L, 80 μM). I-N. Aberrations categorized as simple fusions. I. Centric ring (XPA-L, 100 μM). J. Dicentric chromosome with both centromeres depicted by white arrows (XPB-L, 100 μM). K. Fusion of two terminally broken chromosomal fragments forming a large chromosome-like structure (XPD-L, 40 μM). L. Fusion of two terminally broken chromatid fragments (Normal-L, 20 μM). M-N. Sister chromatid fusions (Normal-L, 20 μM and XPD-L, 60 μM respectively). O-R. Aberrations categorized as complex fusions. O-P. Triradial-like structures (XPA-L, 60 μM and XPD-L, 60 μM respectively). Q-R. Quadiradial-like structures (both from XPA-L, 60 μM). S. Frequency of total aberration per spread following H2O2 treatment. *p < 0.05; **p < 0.01, ***p < 0.001 compared to Normal-L.