Fig. 7. Mitotic pattern and PvuBra expression in ERK inhibited embryos (medium dose). Unless specified otherwise, all views are from the vegetal pole. Presumed D quadrant to the bottom. (A) In situ hybridisation, combined with Hoechst staining of the nuclei, on a 64-cell stage embryo, showing an equalised cleavage pattern (compare with Fig. 3I,J). Sister cells are indicated by a line. (B) 64-cell stage, side views, showing PvuBra expression in 3c¹, 3c², 3d¹, 3d², and at a weaker level, in 2d²² and 2d²¹. No staining is seen in 4D and 4d (the cleavage is equal: compare with Fig. 3B). (C) Late 64-cell stage: some PvuBra expression is now seen in 4D and 4d. (D) Early trochophore: PvuBra expression is detected in cells scattered on the ventral side of the trochophore. pt., prototroche; ft., foot lobe; st., stomodaeum.

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