Practice question

Blocking cortical rotation with UV crosslinks vegetal cortex microtubules preventing dorsal transport of beta-catenin determinants. Without Nieuwkoop center, Spemann organizer never forms, BMP antagonists absent, embryo retains only ventralizing BMP signaling globally. Embryos develop as cylindrical ventralized structures lacking notochord, somites, neural plate and head, termed Bauchstück. Histology shows expanded blood islands, coelom and atypical epidermis expressing ventral markers Vent1/2, Sizzled and Wnt8. Neural and dorsal markers like Sox2, MyoD absent, demonstrating formation of only ventral structures and requirement of rotation for dorsal axis. This illustrates conserved developmental logic of morphogen gradients patterning embryonic axes through Wnt and BMP antagonism.