Chapter 18

Front 1

A microtubule protofilament is formed by the

Back 1

head-to-tail association of tubulin dimers

Front 2

At MTOCs, microtubule nucleation is facilitated by

Back 2

(g)-tubulin

Front 3

Growing microtubule ends are normally stabilized by

Back 3

a GTP cap

Front 4

The drug taxol acts to

Back 4

promote microtubule assembly

Front 5

Microtubule assembly requires

Back 5

tubulin concentration in excess of the Cc

Front 6

MAP2 and Tau are examples of microtubule

Back 6

stabilizing proteins

Front 7

In cells, the (g)-tubulin ring complex is found

Back 7

at the microtubule (−) end

Front 8

The region of a motor protein that interacts with the motor’s cellular cargo is the

Back 8

tail domain

Front 9

Give statements describing kinesin

Back 9

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

Front 10

The ______ serves as a template for the unusual structure of axoneme microtubules.

Back 10

basal body

Front 11

For kinesin motors, the direction of movement along a microtubule is specified by the motor’s

Back 11

neck region

Front 12

Separation of spindle poles during spindle formation and anaphase B most likely depends on

Back 12

end-directed microtubule motors in the microtubule overlap zone

Front 13

What occurs during anaphase A

Back 13

Kinetochores remain attached to shortening kinetochore microtubules

Front 14

In the mitotic spindle, astral microtubules function to

Back 14

allow the spindle to interact with the plasma membrane

Front 15

Treadmilling through kinetochore microtubules can be observed by

Back 15

fluorescence speckle microscopy

Front 16

Kinetochores assemble at the

Back 16

centromere

Front 17

Capture of microtubule (+) ends by chromosomes occurs during

Back 17

prometaphase.

Front 18

Poleward movement of chromosomes during anaphase A requires

Back 18

kinetochore motor proteins

Front 19

In most cells, where do all microtubules originate?

Back 19

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.

Front 20

What is a microtubule protofilament

Back 20

A microtubule protofilament is a head-to-tail assembly of tubulin dimers. Thirteen such structures compose the cylindrical wall of the microtubule.

Front 21

What happens to a microtubule that loses its GTP cap

Back 21

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

Front 22

What is the effect of colchicine or taxol on cells

Back 22

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

Front 23

Why would neuronal vesicles probably contain both kinesin and cytosolic dynein

Back 23

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.

Front 24

What effect will addition of AMPPNP have on axonal transport

Back 24

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

Front 25

What function do kinetochore-bound motor proteins perform during anaphase A?

Back 25

During anaphase A, kinetochore-bound motor proteins are thought to maintain kinetochore attachment to shortening kinetochore microtubules.

Front 26

What role do astral microtubules play in spindle elongation?

Back 26

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.

Front 27

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?

Back 27

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.

Front 28

A characteristic common to all three cytoskeletal systems is

Back 28

they are reorganized during mitosis

Front 29

What occurs during anaphase

Back 29

Kinetochores remain attached to shortening kinetochore microtubules.

Front 30

Capture of microtubule (+) ends by chromosomes occurs during

Back 30

prometaphase

Front 31

ln the mitotic spindle, astral microtubules function to

Back 31

allow the spindle to interact with the plasma membrane