FISH with the telomeric (TTAGG)n probe showed evident telomeric repeats at each chromosomes in clones Mo3 (a), Mo4 (b), Re1 (c) and Re2b (d). No interstitial telomeric signals were present in clones Mo3 (a), Mo4 (b) and Re2b (d) possessing a chromosomes derived from an autosome A1–A3 fusion. All telomeres resulted labelled by the (TTAGG)n telomeric probe in clone Re1 including the X chromosome involved in the fission suggesting that a de novo telomere synthesis occurred in this clone (c). Arrows indicate X chromosomes. Bar = 10 mm.