BSCI-1105 Chapter Notes - Chapter 17, 21: Zona Pellucida, Twin, Granulosa Cell
4 Feb 2020
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These enzymes digest a path for the sperm between the granulosa cells of the corona radiate and through the zona pellucida to the oocyte plasma membrane. Several sperm may be making this journey at the same time: 2. The entry of one sperm triggers the release of enzymes from granules located just inside the egg. These enzymes produce changes in the zona pellucida that make it impenetrable to other sperm: 4. One sperm nucleus, and only one, will enter the egg: the process of fertilization is not yet complete because the egg is still a secondary oocyte; entry of the sperm nucleus triggers the completion of meiosis. 1/90 births: fraternal twins arise from the ovulation of more than one oocyte in a particular cycle; oocytes are different genetically and each is fertilized by a different sperm. Identical twins (maternal twins) arise from a single zygote; always the same gender, and usually closely alike in phenotypic appearance.
