Quick revision: every question with its correct answer. For the full explanation, open the relevant test and tap View Solution.
2.5 Blocks to Polyspermy — Test 1
Q1. Polyspermy (fertilization by more than one sperm) is usually lethal because it produces:✓ Blastomeres with abnormal numbers and types of chromosomes
Q2. The fast block to polyspermy in sea urchins is caused by:✓ A change in egg membrane potential due to sodium influx
Q3. The slow block to polyspermy in sea urchins is the:✓ Cortical granule reaction that raises the fertilization envelope
Q4. The slow block to polyspermy is mediated by which ion?✓ Calcium
Q5. The major function of cortical granules in the egg is to provide the:✓ Slow (late) block to polyspermy
Q6. In mammals, the block to polyspermy is achieved mainly by:✓ The cortical (zona) reaction hardening the zona pellucida
Q7. The cortical granule reaction is triggered by:✓ A rise in intracellular calcium after sperm entry
Q8. Compared with the fast block, the slow block to polyspermy is:✓ Slower to form but permanent
Q9. In sea urchins, the fertilization envelope blocks polyspermy by:✓ Physically lifting away from the egg and hardening
Q10. If an egg has non-functional ovastacin, a likely consequence is:✓ Frequent polyspermy because the zona block fails
Q11. The fast block to polyspermy works by making the egg membrane potential:✓ More positive, so sperm can no longer fuse
Q12. Why do eggs need BOTH a fast and a slow block to polyspermy?✓ The fast block acts immediately while the slow block takes time but is permanent