Biology 2581B Study Guide - Quiz Guide: Zona Pellucida, Vitelline Membrane, Oocyte
1 Jun 2020
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Document Summary
Gametes (egg and sperm) are haploid cells derived from germ cells that undergo meiosis. They are haploid because they only have 1 of each chromosome. When they come together and undergo fertilisation it restores diploidy because the resulting cell has 2 copies of each chromosome. The zygotic genome therefore has 1 maternal copy and 1 paternal copy of each chromosome. Primordial germ cells often develop at an early stage in the embryo - these can be identified, even before the sex of the organism is determined. Sperm are motile cells that are extremely specialised. They have a haploid nucleus, an acrosomal vesicle and a flagellum that allows them to move in search of an oocyte. To create sperm a primary spermatocyte splits into secondary spermatocytes which then split further into spermatids. Eggs are large, specialised cells but they can greatly range in size depending on the organism. For example, a human egg is 100um whereas a frog/fish egg is 1mm.
