Practice question

Classical Spemann-Mangold experiment showed dorsal blastopore lip grafted to ventral side self-differentiates into notochord while instructing host ventral ectoderm to change fate. Organizer secretes BMP antagonists chordin, noggin and follistatin blocking BMP4-induced epidermal differentiation, revealing default neural fate via Sox2 and NCAM activation. Host ventral mesoderm also dorsalized forming somites. Result is secondary embryo with induced neural tube derived from host tissue, demonstrating neural induction and dorsalization. It does not induce epidermal, ventral mesoderm or yolk synthesis functions. This illustrates conserved developmental logic of morphogen gradients patterning embryonic axes through Wnt and BMP antagonism.