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| Description: A. Fertilization most often occurs in the oviduct. Many human sperm travel swiftly through the vaginal canal into oviducts (blue arrows). Inside an oviduct, the sperm surround a secondary oocyte that was released by ovulation. B. Enzymes released from the cap of each sperm clear a path through the zona pellucida. Penetration of the secondary oocyte by a sperm causes the oocyte to release substances that harden the zona pellucida and prevent other sperm from binding. C. The oocyte nucleus completes meiosis II, forming a nucleus with a haploid maternal genome. The sperm’s tail and other organelles degenerate. Its DNA is enclosed by a membrane, forming a haploid nucleus with paternal genes.Later, the two nuclear membranes will break down and paternal and maternal chromosomes will become arranged on a bipolar spindle in preparation for the first mitotic division. Picture Stats: Views: 287 Filesize: 558.27kB Height: 967 Width: 1779 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=47412 |