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Zona Pellucida: Prevents Polyspermy
One sperm: Fertilization Embryonic lethal
Two sperm:
Modifies zona to provide:
• Transient, rapid block to sperm penetration
• Definitive block to sperm binding to the zona matrix
Cortical Granules
CG-free Zone
Cortical granule MTOC
Tubulin spindle Replicated chromosomes
Oocyte-specific
Subcellular organelles
0.2 – 0.6 m diameter
15x increase during oogenesis ~8,000 granules in GV oocytes
Cell Biology of Cortical Granules
CG-free Zone
MII Egg
Fertilization
CG Exocytosis
Gametes Fuse
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