RR Final 9 Mitosis

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RR Final 9 Mitosis
2013-11-23 12:52:35
Cell Bio

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  1.                                                               i.      No obvious change in length of chromosomal microtubules as chromosomes are aligned at the __, studies using __ indicate that the microtubules exist in a highly __
    1.       Subunits are __ and __at the __ of the chromosomal microtubules, even though these ends are attached to the kinetochore
    • metaphase plate
    • fluorescently labeled tubulin
    • dynamic state
    • lost rapidly
    • added 
    • plus ends
  2. a.       Thus, the kinetochore does not act like a __, blocking the entry or exit of terminal subunits, but rather it is the site of __
                                                                                                                                          i.      Because more subunits are added to the __than are lost, there is a __ of subunits at the kinetochore
                                                                                                                                        ii.      Meanwhile, the minus ends of the microtubules experience a __, and thus subunits do what?
    • cap at the end of the microtubule
    • dynamic activity
    • plus end 
    • net addition
    • net loss
    • move along the chromosomal microtubules from the kinetochore toward the pole
  3. When does anaphase begin?
                                                                  i.      Begins when sister chromatids of each chromosome split apart and start their movement toward opposite poles
  4.                                                               i.      Role of Proteolysis in Progression through Mitosis
    1.       __depends to a large degree on __ of __ at precise times during the cell cycle
    2.       Two distinct multiprotein complexes, __, add __to proteins at different stages of the cell cycle, targeting them for __ by a __
    • Orderliness 
    • selective destruction of cell cycle regulatory proteins
    • SCF and APC
    • ubiquitin 
    • destruction by a proteasome
  5. 1.       In contrast, the __, plays a key role in regulating events that occur during mitosis
    a.       The __contains about a dozen __, in addition to an __ that plays a key role in __
    • anaphase promoting complex, or APC
    • APC 
    • core subunits
    • adaptor protein
    • determining which proteins serve as the APC substrate
  6.                                                                                                                                       i.      Two alternate versions of this adaptor protein—__ and __—determine what? during mitosis
    APC complexes containing one or the other of these adaptors are called __ or __
    • Cdc20 and Cdh1
    • substrate selection
    • APCCdc20 or APCCdh1
  7. 1.       __ becomes activated rpior to __ and __a key anaphase inhibitor called __
    a.       The __ and __ of __ at the end of metaphase release an active protease called __, which cleaves the __ of the __molecule holding sister chromatids together 
    • APCCdc20
    • metaphase
    • ubiquitinates 
    • securin
    • ubiquitination and destruction
    • securin
    • separase
    • Scc1 subunit
    • cohesion 
  8.                                                                                                                                       i.      Cleavage of cohesion triggers the __ to mark the onset of __
    1.       Experimental support for the role of __in maintaining the attachment of sister chromatids and their anaphase-like movement towards the poles
    • separation of sister chromatids
    • anaphase
    • cohesion
  9. 1.       Near the end of mitosis, __is inactivated, and the alternate adaptor, __, takes control of the __
    a.       When __ is associated with the __, the enzyme completes the __ of __ that was begun by __
    • Cdc20 
    • Cdh1
    • APC’s substrate selection
    • Cdh1
    • APC
    • ubiquitination
    • cyclin B
    • APCCdc20
  10.                                                                                                                                       i.      Destruction of the cyclin leads to __ and __
    1.       If destruction of cyclin B is prevented with inhibitor, cells are arrested in __
    • a precipitous drop in activity of the mitotic Cdk
    • progression of the cell out of mitosis and into the G1 phase of the next cell cycle
    • last mitotic stage
  11. 1.       Completion of mitosis requires __of activity of __
    a.       When __ are washed free of __, they progress in the __                                                                                                                         
    • cessation 
    • Cdk1
    • Cdk1-inhibited cells
    • Cdk1 inhibitor
    • reverse direction into mitosis
  12. What is the reverse direction into mitosis?
    i.      Compaction of chromosomes, breakdown of nuclear envelope, assembly of a mitotic spindle, movement of chromosomes back to the metaphase plate
  13.                                                               i.      Events of anaphase

    Why is it very slow?
    1.       Chromosomes split and migrate toward poles, led by its centromere with the arms of the chromosome trailing behind

    ensure that the chromosomes segregate accurately and without entanglement
  14. 1.       The poleward movement of chromosomes is accompanied by __
    a.       Lost from the __ of chromosomal microtubules during anaphase
    b.      Subunits are also lost from the __ of these microtubules as a result of __ that occurs during __ and __
    • shortening of chromosomal microtubules
    • plus ends
    • minus ends
    • continued poleward flux of tubulin subunits
    • prometaphase and metaphase
  15.  i.      The primary difference in microtubule dynamics between metaphase and anaphase is what?
    that subunits are added to the plus ends of microtubules during metaphase, keeping the length of the chromosomal fibers constant, whereas subunits are lost from the plus ends during anaphase, resulting in shortening of the chromosomal fibers
  16. 1.       This change in behavior at the microtububle plus ends is thought to be triggered by what?
    the loss of tension on the kinetochores following separation of the sister chromatids
  17. What are the divisions of anaphase?

    When do they occur?
    • anaphase A: movement of chromosomes toward the poles
    • anaphase B: the two spindle poles move farther apart

  18. a.       The elongation of the mitotic spindle during __ is accompanied by the net addition of __ to the __ of the polar microtubules
                                                                                                                                          i.      Thus, subunits can be added to the __ and removed from __ at the same time in different regions of the same mitotic spindle
    • anaphase B
    • tubulin subunits
    • plus ends
    • polar microtubules
    • chromosomal microtubules
  19.                                                               i.      Forces required for Chromosome movements at Anaphase

    1.       Proposed that __of chromosomal microtubules during __was not simply a consequence of chromosome movement but the cause of it; __ of the microtubules that comprise a __ could generate sufficient __ to __
    • depolymerization 
    • anaphase 
    • depolymerization
    • spindle fiber
    • mechanical force
    • pull a chromosome forward
  20. 1.       __ alone can generate sufficient force to __
    2.       During anaphase, the chromosomal spindle fibers undergo what?
    a.       Depolymerization at the minus ends serves to __ due to __
    • Microtubule depolymerization
    • pull chromosomes through a cell
    • depolymerization at both the minus and plus ends
    • transport the chromosoems toward the poles due to poleward flux
  21. a.       Depolymerization at the plus ends serves to __
                                                                                                                                          i.      Some cells rely more on __, others more on __
    b.      Both the plus and minus ends of __ are sites where __ are localized
    • “chew up” the fiber that is towing the chromosomes
    • poleward flux
    • plus-end depolymerization
    • chromosomal fibers
    • depolymerizing kinesins
  22.    i.      If either of these microtubule “__” is specifically inhibited, __ during anaphase is partially disrupted
    1.       Suggests that __ forms the basis for chromosome segregation during mitosis
    • depolymerases
    • chromosome segregation
    • ATp-dependent, kinesin- mediated depolymerization
  23. 1.      __complexes of the kinetochore are present as molecular fibrils that reach out to __ with an attached microtubule just behind its __
    a.       each microtubule is contacted around its circumference by 6 to 9 of these __
    • Ndc80 
    • form relatively weak linkages
    • plus end
    • Ndc80 tethers
  24.        i.      the terminal heads of the __complexes are able to travel along the microtubule towards its __, pushed along by the __ of the disassembling tip
    1.       as a result, the attached chromosome moves toward the spindle pole as it is towed by the shrinking chromosomal fiber
    • Ndc80 
    • minus end
    • curling protofilaments
  25.                                                               i.      Spindle assembly checkpoint
    1.       Operates at the transition between __ and __
    2.       When a chromosome isn’t __, it is delayed until proper position is demonstrated
    • metaphase and anaphase
    • aligned properly at the metaphase plate
  26. 1.       How does a cell determine proper alignment?  
    a.       Unattached kinetochores contain a complex of proteins that mediate the __
                                                                                                                                          i.      The presence of these proteins at an unattached kinetochore sends a __ to the __ that prevents the cell from continuing on into __
    • spindle assembly checkpoint
    • wait signal to the cell cycle machinery
    • anaphase
  27.                                                                                                                                       i.      Once the wayward chromosome becomes attached to __ from both __ and becomes __, the __leaves the kinetochore, which turns off the “__” signal and allows the cell to progress into anaphase
    • spindle fibers
    • spindle poles
    • properly aligned at the metaphase plate,
    • signaling complex 
    • wait
  28. 1.       According to one model, inhibition is achieved through direct interaction between __
    During the period that __is bound to __, APC complexes would be unable to __the __, thus keeping all of the sister chromatids attached to one another by their __
    • Mad2 and the APC activator Cdc20
    • Cdc20 
    • Mad2
    • ubiquitinate 
    • anaphase inhibitor securin
    • cohesion “glue"
  29. 1.       The __ is activated by the presence of an __, but there are other chromosomal abnormalities that arise during the progression to metaphase that also require corrective measures
    a.       __normally develops when sister chromatids are being pulled by microtubules from opposite spindle poles
    • spindle assembly checkpoint
    • unattached kinetochore
    • Tension
  30. 1.       Cells are able to correct __ through the action of an enzyme called __, which is part of a mobile protein complex that resides at the __during prometaphase and metaphase
    • synthetic attachments
    • Aurora B kinase
    • centromere
  31. a.       Among the substrates of __ are several of the proteins thought to be involved in __, including members of the __ and the __
    b.      Studies suggest that __ molecules of an incorrectly attached chromosome __these protein substrates, which does what?
    • Aurora B kinase
    • kinetochore—microtubule attachment
    • Ndc80 complex
    • kinesin depolymerase
    • Aurora B kinase
    • phosphorylate 
    • destabilizes microtubule attachment to both kinetochores
  32.  i.      Once freed of their bonds, the kinetochores of each sister chromatid have a fresh opportunity to __
    Inhibition of __ in cells or extracts leads to __ and __ of chromosomes
    • become attached to microtubules from opposite spindle poles
    • Aurora B kinase
    • misalignment
    • misaggregation