Fig. 5. Visualising mitosis and DNA replication in multicellular development. Mitotic cells were identified using RFP-H2B as a marker for chromatin. These cells were followed for up to 2 hours in the slug stage of development. GFP-PCNA was tracked to identify S-phase cells. The movie is of the prespore region of the slug. The first five frames include both RFP-H2B and GFP-PCNA. The RFP-H2B panels show a cell division in the central cell (arrows). The continuation of the movie (5:00 onwards), showing GFP-PCNA alone, allows one daughter cell (arrows) to be followed into S phase.