470vocabtest2 - Cleavage Terms reductive cleavage a series...

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Cleavage Terms reductive cleavage – a series of rapid mitotic cell divisions following fertilization in many early embryos; cleavage divides the embryo without increasing its mass cytokinesis – division of cell cytoplasm into two daughter cells; each daughter cell receives one of the nuclei produced by nuclear division; mechanical agent is ring of actin microfilaments cleavage furrow – groove formed in the cell membrane in a dividing cell due to tightening of the microfilamentous ring contractile ring – mechanical agent in cytokinesis that pinches cytoplasm; made of actin Rho - astral microtubules polyspermy – entrance of more than one sperm during fertilization resulting in aneuploidy (abnormal chromosome number) and either death or abnormal development cyclin B – larger subunit of MPF; displays cyclical behavior that is key to mitotic regulation, accumulating during S and being degraded after cells have reached M - often encoded by mRNAs stored in oocyte cytoplasm - if translation of this message is inhibited, cell will not enter mitosis cyclin-dependent kinase – smaller subunit of MPF; activates mitosis my phosphorylating several target proteins; actions bring about chromatin condensation, nuclear envelope depolymerization, and organization of the mitotic spindle; requires cyclin B to function MPF – mitosis-promoting factor; consists of cyclin B and p34/Cdk1 cyclin, required to initiate entry into the mitotic (M) phase of the cell cycle in both meiosis and mitosis – in early blastomeres, one of two phases: cyclin B allows progression to M, while degradation of cyclin B allows cells to go to S phase - in somatic cells: M followed by interphase (divided into G1, S, and G2) holoblastic – cell division pattern in the embryo in which the entire egg is divided into smaller cells, as it is in frogs and mammals meroblastic – cell division pattern in zygotes containing large amounts of yolk, wherein only a portion of the cytoplasm is cleaved - cleavage furrow does not penetrate yolky portion of cytoplasm b/c the yolk platelets impede membrane formation there - only part of egg destined to become the embryo, while other portion (yolk) serves as nutrition for the embryo - occurs in insects, fish, reptiles, birds isolecithal – “equal yolk” – describes eggs with sparse, equally distributed yolk particles, as in sea urchins, mammals, and snails mesolecithal – moderate vegetal yolk disposition; displaced radial cleavage; amphibians telolecithal – eggs of birds and fish which have only one small area of the egg that is free of yolk; cell division only occurs in this small disc of cytoplasm centrolecithal – type of egg which have yolk in the center and undergo cell division in rim of cytoplasm - occurs in insects spiral cleavage – annelid worms, some flatworms, and most mollusks; cleavage is at oblique angles, forming a “spiral” arrangement of daughter blastomeres, the cell stouch one another at more places that do those of radially cleaving embryos, assuming most thermodynamically stable packing orientation
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470vocabtest2 - Cleavage Terms reductive cleavage a series...

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