Practice question

Dorsal specification integrates three interacting components: maternally stored Wnt11 mRNA polyadenylated after fertilization secretes dorsalizing ligand activating Frizzled receptors; GBP protein bound to kinesin transported dorsally binding and inhibited GSK-3; Dishevelled scaffold recruited to membrane inhibiting Axin destruction complex. Together they stabilize beta-catenin dorsally activating Siamois and Twin transcription in Nieuwkoop center which activates Nodal. BMP antagonists Noggin and Chordin are downstream organizer products, not dorsal inducers. VegT cooperates for mesoderm induction later. Triad GBP, Dsh and Wnt11 constitutes core dorsal signaling module for axis initiation.