BIOL-4501 Chapter Notes - Chapter 4: Lithium Chloride, Blastocoel, Polarity In Embryogenesis
8 Dec 2016
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Advantages of using specimen: eggs and sperm spawn in high quantities, easy to grow in lab, and transparent embryos. Primordial axis established at fertilization within the egg cytoplasm (animal/vegetal axis). First cleavage is meridonal through poles, second is meridonal through poles, the third is equatorial. Gastrulation will eventually occur at the vegetal plate. Animal tier 1 and 2 become ventral and dorsal ectoderm. Vegetal tier 1 becomes base of archentron and ectoderm. Vegetal tier 2 becomes gut endoderm and secondary mesenchyme. Being placed in new positions, in contact with different cells changed cell fate. Paracrine and juxtacrine factors conditionally specify fate of neighbours. Micromeres in a new position induce a secondary axis with two origins of gastrulation. However, they do not contribute to the vegetal plate. B catenin signals vegetal cells to become endoderm or mesoderm. If inhibited, the embryo will become a ciliated ball of ectodermal cells.
