Visualizing origin licensing by GFP–MCM-3. (A–D) Images taken from time-lapse sequences of embryos progressing through the first (I) and the second (II) meiotic division (left panels) and the first embryonic cell cycle (right panels). Embryos are orientated with the anterior pointing to the top left corner with GFP–MCM-3 (left images in each panel) and mCherry-Histone (right images in each panel). Meiotic divisions are shown at 3x higher magnification. Asterisks indicate polar bodies. Arrowheads point to GFP–MCM-3 chromatin binding in anaphase of meiosis II and mitosis. Diagrams show the enrichment of GFP–MCM-3 signal on chromatin or in pronuclei and nuclei relative to the cytoplasm. Values are plotted over time. Each tick on the x axis represents 5 min. Cell cycle stages are indicated. Bars, 10 µm. (A) Wild-type embryo. (B) mcm-7 RNAi embryo. (C) cdc-6 RNAi embryo. (D) gmn-1 (geminin) RNAi embryo. (E) Mean GFP–MCM-3 chromatin enrichment of five embryos according to cell cycle stage. Error bars are SDs. See also Video 1 for wild type.