BIOS 10161 Lecture Notes - Lecture 17: Extracellular Fluid, Zona Pellucida, Triploblasty
30 Sep 2016
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Document Summary
In addition to producing a diploid zygote, fertilization of an egg by a sperm: blocks entry of additional sperm, stimulates ion fluxes across membrane, changes ph of egg, increases egg metabolism and protein synthesis, initiates cell division. Eggs are large and well stocked with organelles, nutrients, transcription factors, and mrnas aka ready to initiate development. Sperm contributes dna and a centriole to the zygote: centriole becomes a centrosome, which organizes the mitotic spindles for subsequent cell divisions (also origin of primary cilia) Amphibian eggs make good models to show how rearrangements of egg cytoplasm influence determination. Sperm entry establishes polarity of the zygote and molecules in the egg cytoplasm are organized: when cell division begins, informational molecules are not divided evenly among daughter cells. In unfertilized frog egg: vegetal hemisphere lower half of the egg, where nutrients are concentrated, animal hemisphere opposite end of the egg; has pigments and contains the nucleus.
