Telomere length and structure analysis by telomere quantitative fluorescence in situ hybridization (Q-FISH). (A) Representative images of telomere Q-FISH in pig cells. Red rectangle, enlarged region shown in the right column. FF and FM, fetal fibroblast and mesenchymal cells derived from fetus at embryonic day 50, respectively; NF and NM, newborn (7 or 8 days after birth) fibroblast and mesenchymal cells, respectively; AF, adult fibroblasts from the ear skin of an adult pig, 3–4 months after birth. P, passages. Enlarged views: Blue, DAPI-stained chromosomes. Green dots, telomeres; Purple arrows, telomere doublets; P, passage. (B) Histogram shows distribution of relative telomere length shown as telomere fluorescence intensity unit (TFU) in pig cells. Medium telomere length is shown as mean TFU ± SE. The medium telomere length (red bars) is also shown as mean ± SE in the upper right hand corner. Ds, telomere doublets; Chr, chromosomes. Black arrows on the Y-axis indicate frequency of telomere signal-free ends. (C) Representative image of mouse telomeres (green) by Q-FISH. Enlarged view at right. Blue, chromosomes. (D) Telomere distribution and length of mouse embryonic fibroblast at passage 3 (MEFP3).