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Fertilization Terms
| Term | Definition |
|---|---|
| Preformation | the idea that the embryo is already formed and present in the sperm or egg in miniature form |
| epigenesis | idea that an embryo emerges gradually from a relatively formless egg |
| defferentitation | cells become specialized to perform a function |
| morphogenesis | movement of cells and tissue leads to formation of shape and organs |
| Step One | sperm reaches egg; acrosome releases hydrollytic enzymes by exocytosis |
| Step Two | Enzymes activate cytoskeletal elements that elongate the end structure and penetrate the jelly coat of the egg |
| Step Three | Tip of acrosome has proteins that bind to receptors on the vitelline layer just exterior to the plasma membrane. IN some animals, there is a lock and key recognition to assure that they are only fertilized by the proper species |
| Step Four | Egg and sperm plasma membranes fuse |
| Step Five | This causes an electrical response in the egg plasma membrane |
| Step Six | This depolarization prevents other sperm from penetrating the egg (fast block to polyspermy) |
| Step Seven | Fusion also causes vessivles inside egg to exocytosis contents which catalyze a hardening of the extracellular matrix of the cell thus acting as teh slow block to polyspermy |
| Step Eight | In mammals, fusion of egg and sperm nuclei does not occur until after the first mitotic division. |
| Vegetal Pole | end of the egg with the yolk |
| Animal Pole | end of the egg with very little yolk |
| heterogeneous organization of cytoplasm in unfertilized egg | leads to regional differences in the early embryo of many animal species |
| cell-cell interactions | compound differences initiated by cytoplasmic organization and by the elocation of cells during morphogenesis |
| apoptosis | programmed cell death |
| totipotent | a cell that has retained the potential to form all parts of the animal |
| determination | a progressive restriction of a cell's developmental potential |
| induction | the ability of one group of cells to influence the development of an adjacent group of cells |
| tissue-specific proteins | proteins found only in a certain type of cell |
| genomic equivalence | all cells contain the same genes |
| maternal effect genes | phenotypes expressed by these genes are exclusively the product of the mother's contribution usually mutations in genes that are necessary for the egg polarity to be set up properly |
| homeotic genes | genes that determine the anatomical identity of different segments of an individual. |
Created by:
samft98c
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