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31 Cards in this Set
- Front
- Back
A microtubule protofilament is formed by the
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head-to-tail association of tubulin dimers
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At MTOCs, microtubule nucleation is facilitated by
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(g)-tubulin
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Growing microtubule ends are normally stabilized by
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a GTP cap
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The drug taxol acts to
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promote microtubule assembly
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Microtubule assembly requires
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tubulin concentration in excess of the Cc
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MAP2 and Tau are examples of microtubule
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stabilizing proteins
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In cells, the (g)-tubulin ring complex is found
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at the microtubule (−) end
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The region of a motor protein that interacts with the motor’s cellular cargo is the
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tail domain
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Give statements describing kinesin
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Kinesin I transports vesicles along microtubules.
Kinesin I binds and hydrolyzes ATP to produce movement. Kinesin I is composed of two heavy chains and two light chains |
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The ______ serves as a template for the unusual structure of axoneme microtubules.
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basal body
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For kinesin motors, the direction of movement along a microtubule is specified by the motor’s
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neck region
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Separation of spindle poles during spindle formation and anaphase B most likely depends on
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end-directed microtubule motors in the microtubule overlap zone
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What occurs during anaphase A
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Kinetochores remain attached to shortening kinetochore microtubules
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In the mitotic spindle, astral microtubules function to
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allow the spindle to interact with the plasma membrane
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Treadmilling through kinetochore microtubules can be observed by
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fluorescence speckle microscopy
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Kinetochores assemble at the
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centromere
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Capture of microtubule (+) ends by chromosomes occurs during
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prometaphase.
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Poleward movement of chromosomes during anaphase A requires
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kinetochore motor proteins
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In most cells, where do all microtubules originate?
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In most cells, microtubules originate from the MTOC, and the minus ends of the microtubules nucleated by this structure usually remain associated with the MTOC.
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What is a microtubule protofilament
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A microtubule protofilament is a head-to-tail assembly of tubulin dimers. Thirteen such structures compose the cylindrical wall of the microtubule.
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What happens to a microtubule that loses its GTP cap
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Loss of the GTP cap will cause a microtubule to convert from growth to shortening. Shortening will continue until the microtubule disappears or a new cap forms
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What is the effect of colchicine or taxol on cells
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Colchicine blocks assembly of the cell’s microtubules; taxol stabilizes the cell’s tubulin into polymer form. In either case, the normal microtubule dynamics will be disrupted and the cells will be unable to divide
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Why would neuronal vesicles probably contain both kinesin and cytosolic dynein
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Neuronal vesicles may contain both motors so that the vesicle could travel in either direction along a microtubule. Kinesin could carry the vesicle from the cell body to the axon terminus, while dynein could carry the vesicle back to the cell body.
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What effect will addition of AMPPNP have on axonal transport
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Because AMPPNP induces tight binding of kinesin (and most other microtubule motors) to microtubules, vesicle transport would cease because the motors would be locked onto the microtubules
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What function do kinetochore-bound motor proteins perform during anaphase A?
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During anaphase A, kinetochore-bound motor proteins are thought to maintain kinetochore attachment to shortening kinetochore microtubules.
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What role do astral microtubules play in spindle elongation?
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Astral microtubules may serve as “ropes” by which (−) end-directed microtubule motors at opposite sides of the cell cortex reel in the spindle poles and thereby produce spindle elongation.
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During mitosis, the breakdown of the nuclear envelope depends on the disassembly of lamin filaments that form a meshwork supporting the membrane. How is that breakdown accomplished?
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Phosphorylation of nuclear lamins by Cdc2, a cyclin-dependent kinase active in early mitosis, induces their disassembly and prevents their reassembly until the phosphates are removed later in mitosis by specific phosphatases.
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A characteristic common to all three cytoskeletal systems is
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they are reorganized during mitosis
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What occurs during anaphase
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Kinetochores remain attached to shortening kinetochore microtubules.
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Capture of microtubule (+) ends by chromosomes occurs during
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prometaphase
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ln the mitotic spindle, astral microtubules function to
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allow the spindle to interact with the plasma membrane
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