Cell Cycle

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Cell Cycle
2011-09-21 17:51:45
Cell cycle test

Cell Cycle
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  1. _____ (x4) are significant purposes of cell proliferation.
    • Growth of multicellular organism
    • Produce new organisms in unicellular species
    • Generation of offspring
    • Renew aging, apoptotic cells, and damaged tissue
  2. _____ and ____ are the overall control mechanisms of cellular replication.
    Regulation of the timing of nuclear DNA replication and mitosis
  3. _____ are the master controllers of DNA replication and mitotic timing.
    • Small number of heterodimeric protein kinases
    • Cyclin and cyclin dependant kinase
  4. A checkpoint is _____ and can be from an ____ or _____ signal.
    • Stop/Go signal
    • internal or external
  5. _____ is an example of an internal checkpoint signal.
    Kinotochores not attached to spindle microtubules - triggers molecular signal that delays anaphase.
  6. ____ is an example of an external checkpoint signal.
    Growth factors - stimulate transduction machinery that regulates trx of replicative and mitotic proteins.
  7. Density-inhibition is _____.
    Anchorage-dependance is _____.
    • Different ways of regulation the cell cycle
    • Density-inhibition: crowded cells stop dividing (Confluence)
    • Anchorage-dependance: Cell must be attached to a substratum (Most animal cells)
  8. There is a diffusable factor present in _____ cells which causes _____ in cells that come into contact with it.
    • Mitotic cells
    • Nuclear envelope retraction during G1 phase cells and chromosome condensation
  9. _____ are the cell cycle phases which are composed of _____ subphases.
    • Interphase: G1 S and G2 (90% of cell cycle)
    • Mitotic phase: Prophase, Prometaphase, Metaphase, Anaphase, Telophase/Cytokenisis
  10. The cell cycle control system is similiar to a _____ and is regulated by _____ and _____ controls. ____ is the most important checkpoint resulting in _____ if given the "go ahead" or _____ if the cell does not recieve the "go-ahead" signal.
    • Clock
    • Internal and External
    • late G1; completion of S, G2, and M phases and will divide or enter G0 phase
  11. MPF is _____ that is responsible for _____.
    Maturation Promotion Factor is a Cyclin CDK complex that is responsible for cell passage past G2 checkpoint into M phase.
  12. A cyclin is a _____. Cyclins work by ____.
    • Any protein whose concentration rises and falls during the Eukaryotic cell cycle.
    • Forming a complex with CDK, activating them, and determining their substrate speceficity.
  13. _____ are the 3 types of regulators for CDK activity.
    • Kinases/Phosphatases
    • Inhibitory proteins
    • Ubiquitin-Protein ligases
  14. ____ which, _____, is responsible for S-phase initiation.
    • SCF (Skp, Cullin, F-box containing complex), which is a ubiquitin protein ligase that marks s-phase inhibitors p27 and p21 for degredation.
    • (p21, 27 are cCDK inhibitors)
  15. _____ are the 3 early steps of mitosis and are activated by _____ during _____ phase.
    • Nuclear envelope breakdown
    • Remodeling of mitotic spindle
    • Chromosome condensation
    • Mitotic cyclin-CDK's
    • Late G2
  16. _____ is responsible for allowing chromosomes to seperate during anaphase and works by ____.
    • APC
    • Polyubiquinating securin
  17. MPF is a/an _____.
    Cyclin-CDK heterodimer that is the KEY factor in regulating the initiation of Mitosis in all Eukaryotes
  18. Describe regulation of Mitotic cyclin levels.
    • [MPF] high = s phase to M phase. At Metaphase APC/c polyUBq Securin = chromosome seperation.
    • Successful chromosomal seperation = cdc14 activation
    • cdc14 activation = dephosphorylation of cdh1 = activation of APC/c polyUBq of MPF = [MPF] down = telophase begin
  19. Rb is a/an ____ and prevents the cell from _____ by _____.
    • Tumor supressor and prevents the cell from
    • replicating damaged DNA by
    • preventing the cell from progressing from G1 to S phase.
  20. Rb regulates the cell cycles specifically by _____.
    Inhibiting E2F (Rb is an inhibition prot. When bound to E2F it is inactive)
  21. Rb is inactivated by _____.
    Phosphorylation by cCDK complex
  22. E2F is a/an _____ and is responsible for _____. E2F is part of a ____ feedback loop
    • Transcription factor
    • Activating genes required for entry into S phase
    • Positive
  23. Describe mechanism for control of S-phase onset.
    • S-phase cCDK's are inhibited by prot Sic1.
    • [G1 cCDK] increases until there are enough to phosphorylate Sic1.
    • Phosphorylation of Sic1 marks it for polyUbq and proteosomal degredation = S- phase cCDK activation.
  24. The mitotic spindle is _____.
    An accumulation of microtubules that control chromosome movement during mitosis
  25. The centrosome is _____.
    The originating site of the microtubules for for mitosis
  26. _____ is a ____ that holds together sister chromatids.
    • Cohesin
    • A multiprotein complex
  27. Cohesins work by _____.
    • Surround Chromatin and when duplicate DNA is made the helicase passes through the cohesin so both chromatids are inside the cohesin.
    • All cohesins release after G2 accept for a few at the center near the centromere.
  28. _____ is the shortes phase of Mitosis and begins when ____ allowing ____.
    • Anaphase
    • Cohesin proteins are cleaved
    • Kinotochre microtubules to shorten - pulling Chromatin toward opposite poles
  29. Describe mechanism of Cohesin cleavage
    • Seperase is bound by inhibitor protein Securin.
    • When spindle apparatus is properly assembled cdc20 activates APC/c polyUBq activity for Seperase
    • Seperase is activated and Cohesin is cleaved from Chromatids
  30. The nuclear Lamina is comprised of _____ which are comprised of __#__ lamins and arranged in _____ sets of IF. The lamina is broken down by _____.
    • A meshlike network of Lamina intermediate filaments
    • 3 Laminas: A, B, and C
    • 2 perpendicular sets of IF
    • MPF phosphorylates specific serine residues in all three laminas which causes them to depolimerize and the disintegration of the nuclear lamina.
  31. p53 is _____ which also means it is a _____ and is commonly called the "____" because it ____ (x3).
    • Tumor suppressor protein which means it is a trx factor and is commonly called the "gaurdian of the genome" because it:
    • Activates DNA repair protein
    • Inhibits cell cycle at G1/S regulation point
    • Initiates apoptosis if DNA is irreparably damaged.
  32. _____ activates p53. Examples of this include _____.
    • Cellular stress
    • Enviornmental : UV, Chemical agents damaging DNA
    • Anything that compromises the cell genetic integrity.
  33. _____ are the three proteins that p53 activates and their role in cell cylce hault.
    • p21, p27, p57 AKA CIP's (CDK Inhibiter Proteins)
    • They inhibit A-CK2 activity by binding to CDK's and must be degraded before replication can begin.
  34. Disregulation of p53 can be seen in the rare disease _____ where p53 is cannot be exported from the nucleaus for degredation by _____ because of a mutation in _____.
    • Taxia Telangiectasia Mutated (ATM/ATR)
    • MDM2 and MDMX
    • ATM