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2.3 Sea Urchin Fertilization — Test 1
Q1. In sea urchins, chemo-attraction of sperm toward the egg is mediated by peptides such as:✓ Resact and speract
Q2. In sea urchins, sperm direction (chemotaxis) is provided by:✓ Resact
Q3. The species-specific adhesion of sperm to the egg in sea urchins is mediated by the acrosomal protein:✓ Bindin
Q4. In sea urchins, bindin on the sperm binds to its receptor located on the:✓ Egg vitelline membrane
Q5. The correct early sequence in sea urchin sperm–egg interaction is:✓ Chemo-attraction → acrosome reaction → binding to egg coat → penetration → membrane fusion
Q6. In sea urchins, exocytosis of the sperm acrosomal vesicle releases:✓ Enzymes that help the sperm penetrate the egg coats
Q7. In the sea urchin egg, the molecule that releases Ca2+ from intracellular stores at fertilization is:✓ Inositol 1,4,5-trisphosphate (IP3)
Q8. IP3 formed at the site of sperm entry in the sea urchin egg triggers:✓ Release of sequestered Ca2+ and cortical granule exocytosis
Q9. During the sea urchin 'respiratory burst' at fertilization, cross-linking of the fertilization envelope is accompanied by a calcium-dependent rise in:✓ Oxygen consumption
Q10. Adding resact to seawater containing sea urchin sperm will:✓ Specifically attract sperm of the same species
Q11. In the sea urchin egg, a rise in intracellular Ca2+ at fertilization promotes:✓ Docking and fusion of cortical granules with the egg membrane
Q12. In sea urchin eggs, blocking PLC-gamma can be bypassed (fertilization rescued) by microinjecting:✓ IP3
2.3 Sea Urchin Fertilization — Test 2
Q13. The fertilization envelope in sea urchins is formed from the:✓ Raised vitelline layer after cortical granule release
Q14. A rise in cytosolic calcium just after fertilization in a sea urchin egg leads to:✓ Formation of the fertilization envelope
Q15. The last of the following to occur after a sea urchin sperm binds the egg is:✓ Initiation of new mRNA synthesis
Q16. Which statement about sea urchin fertilization is correct?✓ The slow block to polyspermy is accomplished by the cortical granule reaction
Q17. The acrosome reaction in sea urchin sperm is triggered by contact with the:✓ Egg jelly coat
Q18. Bindin receptors on the sea urchin egg vitelline membrane ensure that:✓ Only sperm of the same species bind and fertilize
Q19. Removing the bindin receptors from the sea urchin egg vitelline membrane would:✓ Prevent species-specific sperm binding and block fertilization
Q20. The 'fast block' to polyspermy in sea urchins involves a change in the egg's:✓ Membrane potential, caused by sodium influx
Q21. Speract and resact increase sea urchin sperm:✓ Motility and respiration as well as guiding them to the egg
Q22. In sea urchins, the cortical granule reaction is set off by:✓ The rise in intracellular calcium after sperm entry
Q23. The overall role of the cortical granule reaction in the sea urchin egg is to:✓ Establish a permanent (slow) block to polyspermy