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33 Cards in this Set
- Front
- Back
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Aster |
sperm with two centrioles - centrosome - microtubules extend from this |
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Fusion of genetic material |
Aster forms Sperm mitochondria and flagellum disintegrate Dissolution of sperm nuclear envelope Decondensation of male chromatin, swap packaging for egg proteins Difference between mammal and sea urchin is timing |
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Sea urchin fusion |
Sperm enters perpendicular to egg, Contributes nucleus and centriole, Female pronucleus is eccentric, Fusion initiates cortical granule exocytosis, Sperm enters, centrosome activated, microtubules move pronucleuses together, fuse to diploid, DNA replication, centrosome duplicates, organizes mitosis |
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Mammal fusion |
Takes longer, M2, sperm enters sideways, several Ca2+ waves, one starts meiosis, DNA is uncompacted, DNA replication in both pronuclei while migrating, centrosome duplicates, almost two cells before diploid nucleus |
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What is determined during cleavage and gastrulation |
Cell fate and embro axis |
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Cleavage |
Rapid cell division NOT accompanied by cell growth - more cells (blastomeres), less volume Cleavage furrow determined by sperm entry Egg protein and RNA control this |
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maternal mRNA test |
Shows that maternal RNA is used for translation Actinomycin D added to inhibit transcription but translation is till happening |
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Mitosis promoting factor |
Drives cleavage Subunits Cyclin B and cdc 2 Cyclin B upregulates cdc2 (protein kinase) Cdc2 phosphorylates several factors - chromatin condensation, organization of mitotic spindle Cyclin B regulated by remaining factors |
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Mid Blastula Transition |
aka maternal to zygotic transition embryonic genome starts to get utilized maternal factors in cytoplasm are used up |
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Karyokinesis |
Mitotic division of nucleus |
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Cytokinesis |
Physical division of the cell |
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Contractile ring |
actin filaments perpendicular to mitotic spindle aka tubulin microtubules Create cleavage furrow |
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Cleavage pattern is determined by |
1. Amount and distribution of yolk - where cleavage can occur and size of blastomeres 2. Factors in the egg cytoplasm - angle of mitotic spindle |
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Based on whether daughter cells are completely seperated |
Holoblastic - complete separate cells, not much yolk Meroblastic - incomplete separation - massive yolk |
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Based on position or amount of yolk |
Isolecithal - uniform yolk distribution - holo Mesolecital - moderate yolk - holo Telolecithal - one end - mero Centrolecitahal - centre - mero |
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Based on positioning of mitotic spindle |
Radial Spiral Bilateral Rotational Discoidal Superficial |
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Holoblasic - Isolecithal --> Raidal, spiral, bilateral, rotational Holobalstic - Mesolecithal --> Displaced radial cleavage Meroblastic cleavage - Telolecithal --> Bilateral, Discodial Meroblastic - Centriolecithal --> Superficial |
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How do cells and tissues know how to develop |
Through mutual interactions- induction and competence Context of their environment - position in body and neighbor cells |
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Cell fate determined by |
1. Asymmetric cell divisions 2. Cell to cell interactions 3. Cell-cell communications 4. Position of the cell in an embryo |
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Asymmetric cell divisions |
From cells that have different cytoplasm determinants, significant during early cleavage, unequal distribution of maternal mRNA and maternal proteins in cytoplasm |
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Asymetric Patterning Molecules |
Bound to egg cytoskeleton on only one side - two different cell shapes Transported along cytoskeleton - different metabolic activity or motility Associated with centrosome - influence mitotic spindle formation |
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Symmetric division |
Different daughter cells based on cell-cell interactions and cell-cell comunications |
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Cell-cell interactions |
Tight junctions - sheets of cells Anchoring junctions - cytoskeletons of adjacent cells Communicating junctions - small molecules can pass between gap junctions (animal cells) or plasmodesmata (plant cells) |
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Cell-cell communications |
Induction - usually close range between two or more cells and tissues Inducer - produces/ sends signal morphogen Responder - target cell must be capable of responding via receptor for morphogen Competence - response ability at that time |
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Instructive or Permissive induction |
Instructive - signal is necessary to initiate new gene expression Permissive - responder has already been specified, environment that allows expression of traits |
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Morphogen |
Signaling molecule Ligand, ion, hormone, protein, polypeptide growth factor Produced by inducer Directs fates by varying in concentration Positional information leads to pattern formation |
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Juxtacrine Paracrine Endocrine Autocrine |
Direct contact Neighboring cells Hormones Paracrine factor |
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Morphogen gradients |
conduct proliferation and differentiation through concentration gradient control 2D cell polarity |
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Signal transduction systems |
1. Receptor has enzymatic activity - tyrosine kinase 2. Receptor coupled to heterotrimeric G protein -GPCRs 3. Intracellular receptors - cytoplasm or nuc 4. Channel linked receptors - ionotropic |
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Receptor with enzymatic activity |
Ligands - protein hormones or paracrine factors Ligand binds, receptor activation through dimerization and autophosphorylation Activated receptor adds phosphate to tyrosine Cascade |
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Kinase cascade |
Series of protein kinases that phosphorylate eachother in succession Amplifies as they go e.g.) Mitogen-activated protein kinases |
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G Protein Cell Signaling |
Ligand binds to receptor, binds to inactie G protein, alpha sub switches GDP for GTP, G protein activated Alpha detaches, binds and activates effector, cellular response |
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Intracellular receptors |
Hydrophobic ligand easily passes through membrane Binds to receptor in cytoplasm or nucleus and changes conformation Receptor is transcription factor and changes gene expression |
