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23 Cards in this Set
- Front
- Back
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Is there a unique quiescent state?/Are cells that --> quiescence thru various means in same state? |
Studies of kinetics of cells re-entry from quiescence --> S phase under different conditions indicate a single switching point, the Restriction point (R point) in G1 |
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What hypothesis does evidence suggest about a functionally short-lived regulator protein? |
That it needs to accumulate to a critical amount before it can pass the R point and proceed towards DNA synthesis, which is sensitive to environmental conditions |
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What observations led to the discovery that platelet derived growth factor (PDGF) is a key mitogen in serum? (mitogen = induces/stimluates mitosis) |
That plasma, lacking the platelet products contained in sperm, does not support proliferative growth of cells |
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What two things (what are they?) are required for cells to proliferate?) What does this probably mean? |
Require both PDGF and Platelet Poor Plasma Means it's likely that they control different events in the cell cycle |
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What did experiments with PDGF and PPP added at different times confirm? |
That they work at different points in the cell cycle |
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Experiment on PDGF and PPP |
Cells treated with PDGF & PPP --> DNA synthesis after 12 hours Cells for 5 hrs with PDGF then washed free don't enter S phase w/o PPP Addition of PPP later --> cells enter S phase 12 hours after addition of PPP |
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What does PDGF induce cells to become competent of? What did the experiment mean for their control of the cell cycle? |
PDGF induces them to become competent to synthesize DNA PDGF and PPP control different events in the cell cycle |
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Which cells do elements in PPP allow to progress through G0-G1 aand enter S phase? PDGF is therefore referred to as what? Plasma contains what factors? |
Elements in PPP allow competent, not incompetent cells to enter S PDGF is competence factor; plasma contains progression factors |
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What else was identified as a competence factor? (What even is a competence factor??) |
Fibroglass Growth factor |
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What does adding antibodies to insulin-like growth factor block?
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Stimulation of DNA synthesis by human plasma or calf serum |
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What did adding antibody at progressively later times during G1 demonstrate? |
That cells escape from dependence on IGF-1 after traversing G1 to a point near G1/S boundary |
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EGF also plays important role in progression. If PDGF treated competent cells are placed in medium with EGF + IGF-1 what happens to the cells? |
They synthesize DNA as effectively as seen in presence of plasma |
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What allowed the cells to enter S phase?
What does the fact that this does not allow cells to complete the full cell cycle suggest? |
Addition of PDGF to cells for 4-5 hrs followed by exposure to EGF and IGF-1 That additional factors are required for completion of G2 and/or Cell division |
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Cell Cycle genes: Cdc genes and cell cycle regulation in yeast- Saccharomyces cerevisiae |
Budding yeast, differs from mammalian cell cycle in having no G2 (NTK?) |
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Schizosaccaromyces pombe |
Fission yeast, similar to mammalian cell cycle |
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Yeast "start genes" What are cdc28, 36, 37, 39 required for in budding yeast? |
to traverse start |
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Cdc2 and cdc10 genes are required to traverse start in what kind of yeast? |
Fission yeast |
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What do genes in G2 act to determine? (in fission yeast (?)) |
dtermine cell cycle timing of mitosis |
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Biochemical Properties of cdc2 Protein Product- |
-cdc2 gene encodes for a 34 kDa protein -Cdc2 protein is a phosphoprotein which has protein kinase activity. -Mutations that disrupt cdc2 kinase activity abolish cdc2 gene function -When cells are in a non-proliferative state cdc2 protein is not phosphorylated and it loses its kinase activity. |
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Oocytes stimluated by hormones/fertilization and releasedfrom G2 arrest enter what phase? WHat is the key to this transition? What can drive recipient G2 arrested oocyte into M phase? |
M phase Development of Matruation Promotion Factor (MPF) in cytoplasm MPF taken from a fertilized egg |
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What did isolation and purification of MPF show? |
Had 2 subunits, one 32 kDa protein; 45kDa protein, CDC2 and cyclin B respecctively |
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When does cyclin B rise and peak? (which phases) What happens to it at the end of M phase? |
rises thru S phase, peaks during M phase drops dramatically at end of M induces kinase activity of MPF |
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Each cyclin has a distinct time course. What is Cyclin D1's?What does it increase in response to? Build up of cyclin D1/interaction with CDK 4/6 is under control of what? What do other cyclin variations represent? |
Rise throughout G1- moves cells past R point Growth factors Control of external agents (growth factors, environmental conditions) others represent cell-autonomous program |
