2)spermatozoa fuse with the membrane of ovum: nucleus enter cytoplasm of ovum 3)monospermy cortical reaction: cortical granules(located in cytoplasm of ovum)/are released into perivitelline space, and cause zona reaction: change of ZP3 molecules in zona pellucid 4) formation of zygote(fertilized ovum secondary meiosis complete: form second polar body male pronucleus fuse with female pronucleus, to restore the 2n chromasome2) spermatozoa fuse with the membrane of ovum: nucleus enter cytoplasm of ovum 3) monospermy: cortical reaction: cortical granules(located in cytoplasm of ovum) are released into perivitelline space, and cause zona reaction: change of ZP3 molecules in zona pellucide 4) formation of zygote(fertilized ovum) secondary meiosis complete: form second polar body male pronucleus fuse with female pronucleus, to restore the 2n chromasome