Figure 7.

ZM blocks the formation of normal chromatin structures independently of spindle assembly. (A) Cycling egg extracts were incubated with DMSO (control), nocodazole (10 μg/ml), or 20 μM ZM on ice. Extracts were supplemented with nuclei (500/μl) and then warmed to 21°C to resume cycling. At the indicated times, samples were fixed and chromosomes were visualized by staining with Hoechst 33042. The images shown are representative of the most abundant chromatin structures observed at the indicated times. Magnification, 100×; bar, 10 μm. (B) Quantification of chromatin structures from A. The number of chromatin groups that appeared to be fully condensed into discrete chromosome threads at 65 min was determined for DMSO-, nocodazole-, or ZM-treated extracts. More than 100 nuclei were counted for each sample. (C) Quantification of the number of condensed chromosomes from A. The number of chromatin groups that contained condensed chromosomes at 75 min was determined for DMSO-, nocodazole-, or ZM-treated extracts. More than 100 nuclei were counted for each sample.