Terms (definitions) for Establishment of cells and tissues (here use lens cells as an example) Competence, wherein cells can become lens precursors if they are exposed to the appropriate combination of signals. Specification, wherein cells have received the appropriate signals to become lens precursors, but progression along the pathway to lens can still be repressed by other signals. Commmitment (determination), wherein lens precursors have entered a differentiation pathway, and will become lens even in the presence of inhibitory signals. Differentiation, wherein the lens cells leave the mitotic cycle and express those genes characteristic of their cell type.
Early dpp/BMP gradients dictate the D/V axis of the entire embryo
Figure 23.14 Homologous Pathways Specifying Neural Ectoderm in Protostomes (Drosophila) and Deuterostomes (Xenopus) D/V Early dpp/BMP gradients dictate the D/V axis of the entire embryo
Later cases of dpp/BMP expression direct specific embryonic tissue inductions