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BIOL 3P28-Final exam notes.docx

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Robert Carlone

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BIOL 3P28Final Exam Notes CHAPTER 5 Blastomerea cell derived from cleavage in an early embryo Blastulacomposed of blastomeres The cavity within the blastula is the blastocoel Stereoblastulablastula lacks a blastocoel BlastocystA mammalian blastulaBlastoporeinvagination where gastrulation begins Deuterostomesanus echinoderms tunicatesvertebratesprotostomes mouth Blastocoelfluidfilled cavity forms in animal hemisphere of early amphibian and echinoderm bw the epiblast and hypoblast of avian reptilian and mammalian Convergent extensioncells merge to narrow the tissue and to move it forwardthe sea urchinfor elongation of the archenteron amphibianinvoluting mesodermFertilization to cleavageResumption of mitosis and cell division after fertilization by synthesis and degradation of cyclin B o promotes the formation of mitosispromoting factor and MPF promotes mitosis highest during MDegradation of cyclin B brings the cell back to S phase G phases are added at the midblastula transitionMPF composed of two subunits o cyclinBsynthesis messages is due to egg cytoplasm mRNA until the midblastula transition o Cyclindependent kinaseCleavage Karyokinesismitotic division of cell nucleusMitotic spindle of tubulinCytokinesisdivision of the cell Contractile ring of actin microfilaments creates cleavage furrowmost species except mammals rate and pattern of cell division is controlled by maternal gene products in eggRaBo of nuclear volumecytoplasmic volume increases during cleavage Cell divisions rapidno G1 orG2 Patterns of cleavage are dependent on A Amount and distributionof yolk in eggB Cytoplasmic factorsinfluence the angle of the mitotic spindle and the timing of its formationHoloblastic complete cleavageIsolecithalSparse evenly distributed yolk o Radial cleavageEchinoderms amphioxus o Spiral cleavageAnnelids molluscs o Bilateral cleavageTunicatethe first cleavage plane establishes the rightleft axis of symmetry o Rotational cleavageMammals nematodesMesolecithalModerate vegetal yolk disposition o Displaced radial cleavageAmphibiansMEROBLASTIC INCOMPLETE CLEAVAGETelolecithalDense yolk throughout most of cello Bilateral cleavageCephalopod molluscs o Discoidal cleavageFish reptiles birdsVegetal poleslow division yolk rich Animal polefast division yolk freeGastrulationtypes of cellular movementso Invagination The infolding of cells like the indentingsea urchin o Involution inward movt of expanding outer layerspreads over internal surface of remaining external cell o Ingression migration of cells from the surface layer into the interior of the embryobecome mesenchymalo Epibolymovt of epithelial sheets ectodermal cells spread as a unit to enclose deeper layers of embryoCell specification and axis formation o cell fates occur during cleavage through cellcell interactions or cytoplasmic segregationo AP head to tail mouth to anus DV back to belly RL axis two lateral sides of the body
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