Distribution of telomeres in late 1-cell stage embryos. 3D-FISH was performed with telomeric (blue), pericentromeric (red), and centromeric (green) probes; DNA is in grey. (A, B) Single confocal images of PN5 embryos (collected at 27 hphCG). Telomeres are found 1) at the NPBs’ periphery, 2) associated with extra nucleolar centromeric/pericentromeric signals (A insert), or 3) free in the nucleoplasm (B). (C, D) In embryos at prophase (collected at 30 hphCG), the “cartwheel” organization of condensing chromosomes can be observed in both the fPN (C) and mPN (D). In C/D, four successive confocal sections were merged to improve chromosome visualization. Bars = 5 μm.