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Review the sequence of fertilization, beginning with sperm ejaculation and ending with the formation of the zygote.
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Correct answer:
Of the many sperm that enter the uterus, only a few hundred reach the site of fertilization within the oviduct. These sperm cells undergo capacitation, a process that removes their glycoprotein coats, charges the sperm cell membrane and allows the acrosome reaction to occur. The acrosome reaction involves the activation of ZP3 and ZP2 enzymes and enables the sperm cell to penetrate the zona pellucida of the egg cell. The sperm membrane and egg membrane fuse, after which the sperm nucleus enters the egg cell. The sperm and egg nuclear membranes break down and reform as the male and female pronuclei. Haploid DNA synthesis begins at this point, the pronuclear membranes break down and the parental DNA mixes to form the zygote.
