Practice question

Following sperm entry, a parallel array of microtubules assembles in vegetal cortex and motor proteins drive rotation of outer cortical cytoplasm about thirty degrees relative to inner cytoplasm. This cortical rotation translocates maternal dorsal determinants including Dishevelled, GBP, and Wnt11 RNA toward the side opposite sperm penetration. The less pigmented area appearing there is called gray crescent, marking future dorsal side. It accumulates stabilized beta-catenin essential for Nieuwkoop center formation, organizer gene expression, and dorsal lip development. Position predicts embryonic axis.