Multiple choice

In mammals, the prevention of polyspermy ensures that the diploid zygote is protected. Which of the following mechanisms is involved in the process of polyspermy?

  1. Resumption of the second meiotic division of the egg

  2. Activation of the polar body to begin mRNA synthesis

  3. Depolarization of the egg membrane by a rise in intracellular calcium

  4. Initiation of the acrosome reaction in the sperm

  5. The zona pellucida is modified by serine proteases that are released from the cortical granules
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C Correct answer
Explanation

During fertilization, a sperm cell penetrates an oocyte (egg); fusion of sperm and oocyte membranes drives an increase in intracellular calcium in the oocyte. This fusion and rise in calcium causes depolarization of the egg membrane which prevents other sperm cells from fusing with the egg cell (this is the primary block to polyspermy).

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