Fig. 4.

Mitotic chromatin decondenses temporarily during DNA replication. Sperm chromatin was incubated with egg cytosol containing (C, G, E, I, K, and M) or lacking (B, F, D, H, J, and L) geminin for 20 min. Subsequently, Cdk1/cyclin B was added to render the chromatin mitotic. After 40 min, reactions were supplemented with 2 volumes of NPE containing (D, E, H, and I) or lacking (B, C, F, G, and J--M)50 μg/ml aphidicolin. Some reactions contained bio-dUTP (J-M). Samples were withdrawn before (A), 2 min after (B-E), 10 min after (F-I), or 30 min after (J-M) NPE addition. Samples were stained with Hoechst (A-K) or with fluorescently labeled streptavidin (L and M) and visualized.