lecture 29 W11 - Lecture 29 Notes I Fertilization fusion of...

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Lecture 29 (3-25-10) Notes I. Fertilization – fusion of two highly specialized cells A. Sperm – a long cell with an acrosome at the head, a haploid nucleus, a centriole, some mitochondria and a long flagella. B. Egg – huge in size, containing a haploid nucleus, lots of maternal mRNAs. 1. Besides the normal assortment of organelles, eggs have specialized cortical granules, secretory vesicles docked at the plasma membrane 2. The egg is covered by a protein-rich vitelline envelope and a much thicker, gelatinous jelly layer 3. Sea urchins are a great system for studying animal fertilization because they release their gamates into open sea water. In the lab, one can obtain large quanities of both sperm and eggs. C. Sequence of fertilization 1. Upon contact with the jelly layer, sperm undergo the acrosomal reaction. The acrosome fuses with the sperm plasma membrane, releasing enzymes that soften the jelly layer. 2. In addition, the sperm actin reorganizes into the acrosomal process (the tip of the spear for the penetrating sperm). 3. Sperm docks on the egg vitelline envelope 4. Sperm membrane fuses with the egg membrane, and the sperm nucleus is deposited into the egg cytoplasm. The sperm and egg nuclei fuse, forming the zygotic diploid nucleus. C. Sperm-egg recognition 1. Requires specific protein-protein interactions between a sperm and an egg transmembrane protein. 2. To isolate the protein on the egg surface required for sperm recognition, researchers subjected eggs to limited proteolysis to remove portions of the proteins on the surface. 3. These protein fragments were then incubated with sperm, to see which one could block sperm from fertilizing eggs. 4.
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This note was uploaded on 02/13/2012 for the course BIO 172 taught by Professor Clark during the Winter '08 term at University of Michigan.

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lecture 29 W11 - Lecture 29 Notes I Fertilization fusion of...

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