Distribution of pericentromeres and telomeres at different stages of mouse preimplantation development. 3D-FISH was performed with telomeric (blue) and pericentromeric (red) probes; DNA is in grey. Representative single plane confocal images are presented for: early and late 2-cell embryos (A, B) early and late 4-cell (C, D), early and late 8-cell (E, F), 16-cell (G), and blastocysts (H). As expected, only half of the telomeres are associated with pericentromeric signals. . Note that at the blastocyst stage we randomly analyzed the trophectoderm cells and the inner cell mass. B. Bars = 5μm.