Fig. 2. Metasynchronous mitoses occur prior to cycle 10. (A-F) are images from a time-lapse recording of a histone-GFP embryo at cycle 7. All nuclei are at the beginning of interphase (A) and then enter prophase (B). (C) The nucleus in the posterior region enters anaphase (black arrow), while the one in the middle (white arrow) remains in metaphase and enters anaphase 40 seconds later (D). (E) Both nuclei are in telophase. The two daughter nuclei in (E) moved out of the focal plane but all other nuclei show early interphase configuration of cycle 8 at the same time (F). That nuclei in different regions enter interphase at the same time is supported from other time-lapse recordings. (G) Summary of the regional differences of cell-cycle-phase durations in histone-GFP embryos at cycle 7 (n=9) and cycle 8 (n=17), showing that prophase-metaphase is longer and anaphase-telophase is shorter in the middle region than in the posterior region. The total cell cycle time at cycle 8 is not significantly different in the two regions. (H) An epifluorescence image showing metasynchronous mitoses at cycle 7 from a fixed wild-type embryo: nuclei at the two polar regions are in anaphase, whereas the nuclei in the middle region are in metaphase. Scale bars: 100 µm.