A) Draw and describe the Wnt signal transduction pathway i) with and ii) without ligand binding. Follow the molecules from the receptor, all the way into the nucleus. B) Summarize the formation of the dorsal axis in the Xenopus embryo beginning with the oocyte and proceeding through to the late blastula. Indicate where Wnt signaling is and is not activated. C) Explain the changes in gene expression that occur after Wnt activation and how these affect organizer genes and gastrulation. This is a developmental biology/embryology question. If you don’t understand it, please let someone else answer it.