Interphase FISH distance measurements on interphase nuclei from G₀ fibroblast cells to determine the distance between either the 9p or the 12p telomere probe and the corresponding probe for the most distal marker. Telomere probes are shown labeled in digoxigenin and detected with anti-digoxigenin rhodamine (red); probes for the most distal makers are shown labeled in biotin and detected with avidin–FITC (green). The arrowheads show hybridization signals for each probe set from a single nucleus. Bar, 5 μm. (A) Hybridization of clone RG41L13 (9p telomere, red) and clone GS56N11 (AFM274XE1, green); the genomic distance is estimated to be 250 kb between these two probes. Notice the close proximity of the green and red signals for the 9p clones. (B) Hybridization of clone GS8M16 (12p telomere, red) and clone GS93E1 (AFM303XD9, green); the genomic distance is estimated to be 600–800 kb between these two probes. Notice the greater signal separation between the 12p clones as compared to the 9p clones.