Practice question

Chordin similarly binds BMPs via cysteine-rich von Willebrand domains sequestering ligands extracellularly. Ventral overexpression creates ectopic zone where BMP signaling abolished, allowing ventral marginal zone cells to adopt dorsal mesoderm fate expressing MyoD, collagen and forming notochordal tissue, while overlying ventral ectoderm neuralizes expressing NCAM. Neighboring cells recruited into secondary axis complete with somites and neural tube mirroring Spemann graft secondary axis induction. Ventralization never results from BMP antagonists. Therefore injection with chordin induces secondary axis phenocopying organizer transplantation demonstrating sufficiency. This illustrates conserved developmental logic of morphogen gradients patterning embryonic axes through Wnt and BMP antagonism.