The slow block to polyspermy involves a permanent modification of the egg surface, usually through exocytosis of the cortical granules. In the 1970s, Dave Epel carried out experiments that led to the conclusion that a Ca2+ rise in the egg is both necessary and sufficient to trigger cortical granule exoctyosis (CGE). For the experiment below, describe it as correlation, loss-of-function or gain-of function. Then, indicate the predicted result.
Experiment (a) – Dr. Epel injects the egg with an indicator dye that fluoresces when Ca2+ binds to it. In unfertilized eggs, there is no fluorescence and no CGE. However, when sperm are added to the eggs, he observes fluorescence and then CGE.
In biology, polyspermy states an egg that has been fertilized by more than one sperm.
Diploid organisms normally contain two copies of each chromosome, one from each parent. Thus, only one sperm fuses with the egg cell.
There is certain modification in the outer most zona pellucida layer of the egg cell after the first sperm fuses with the egg cell. This modification ensures that there is no other sperm cell fusion with the egg cell.
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