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During the fusion stage in human fertilization, which of the following would you NOT expect to occur?
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Correct Answer: D. Blending of the pronucleus from the ovum and sperm into one.
The blending or fusing of the pronuclei from the oocyte and the sperm cell does not occur, in that the two do not become one. What does occur is that the protective membranes on both dissolve, allowing for the genetic material to co-mingle. A mitotic spindle is formed and attaches itself to the chromosomes from each pronucleus before the chromosomes are fully dispersed throughout the cytoplasm of the oocyte. Mitosis then takes place creating daughter cells that are genetically identical. You may remember that all of a female’s eggs are arrested at meiosis II. The eggs remain in this stage until sperm fertilizes them.
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