Practice question

Egg activation is series of events initiating embryonic development after sperm entry, including cortical granule exocytosis, resumption of meiosis, pronuclear formation and maternal mRNA recruitment. Primary trigger is repetitive intracellular calcium oscillations generated by sperm-introduced phospholipase C zeta hydrolyzing PIP2 to IP3, releasing calcium from endoplasmic reticulum. Calcium wave activates CaMKII, degrades cyclin B, reduces MAPK activity and triggers zinc spark. Sodium, potassium or magnesium influx cannot initiate this cascade; calcium-calmodulin signaling is universal activator conserved from sea urchin to mammals, linking fertilization to developmental program onset.