Lecture 42 Cell Division And Apoptosis

Front 1

Which end of the mitotic spindle microtubule is located at the centrosome

Back 1

the minus end

Front 2

Which end of the mitotic spindle microtubule polymerizes away from the microtubule?

Back 2

the plus end

Front 3

The kinetochore on the chromosome binds to which end of the mitotic spindle microtubule

Back 3

The kinetocore binds to the plus end of the microtubule forming a kinetochore microtubule

Front 4

How do chromosomes induce microtubule assembly

Back 4

It invovles Ran, a GTP binding protein. The Ran-GTP complex interacts with importin leading to the release of importin bound proteins that promote microtubule assembly. Ran-GTP helps organize the newly forming spindle and guide the attachment of microtubules to chromosomal kinetochores

Front 5

Describe the two forces exerted by kinetochore microtubules

Back 5

1. push chromosomes away it they approach either pole
2. pull chromosomes toward the pole that the microtubule is attached to

Front 6

How do the two forces exerted by the kinetochore microtubules ensure that the chromosomes remain alinged in the center of the metaphase plate?

Back 6

the two forces balance each other exactly

Front 7

What motor proteins are associated with moving chromosomes (via their kinetochores) to the opposite pole of the cell

Back 7

kinesin family motor proteins

Front 8

Describe how kinesins move chromosomes to the opposite poles of the cell

Back 8

The kinesins bind to the end of a microtubule and induce it to depolymerize.

Front 9

Describe the role of the motor proteins at the plus end of the kinetochore microtubule in moving chromosomes to each side of the cell

Back 9

The plus end kinesisn "chew up" (depolymerize) the plus ends of the microtubule. This pulls the chromosome toward the spindle pole as teh kinetochore MTs are shorted through the loss of tubulin subunits.

Front 10

Describe how the motor protiens at the minus end of the kinetochore MTs facilitate the movement of the chromosomes to the spindle poles.

Back 10

The minus end motor proteins depolymerize the MT and "reel in" the chromosome

Front 11

During anaphase, the spindle poles must move away from each other to ensure proper chromosome separaton. Explain how motors involved with polar microtubules make this happen

Back 11

Motor proteins cross link the polar MTs and cause them to slide apart. This forces the spindle poles away from each other. As the polar MTs slide apart, they are lengthened by the addition of tubulin subunits at their plus ends near the spindle center.

Front 12

Explain the role of astral microtubule motor proteins in mitosis.

Back 12

Astral microtubule proteins link the plus ends of astral MTs to the cell cortex and exert a pull on the spindle poles by inducing depolymerization. This also helps spindle pole separation.

Front 13

What are the three groups of motor proteins invovled in mitosis

Back 13

1. kinetochore microtubules
2. polar microtubules
3. astral microtubules

Front 14

What forms the contractile ring that facilitates cell clevage during cytokinesis

Back 14

a bundle of actin microfilaments

Front 15

How is the contractile ring tightened during cytokinesis

Back 15

Myosin motor proteins interact with the actin microfilaments

Front 16

Explain the role of the Rho family GTP binding protiens, specifically RhoA, in cytokinesis

Back 16

RhoA activates proteins taht promote actin polymerization and stimulates protein kinases that phosphorylate myosin which activates myosin to tighten the contractile ring.

Front 17

What occurs during anaphase A?

Back 17

chromosomes move to spindle poles

Front 18

What occurs during anaphase B?

Back 18

The spindle poles separate

Front 19

Breifly describe what each type of MT motor does in anaphase
kinetochore
astral
polar

Back 19

kinetochore- move chromosomes to pole
astral- pull on spindle poles that helps to separate them
polar- push- slide MTs, move spindles away from eachother

Front 20

Latrunculin binds actin monomers at the contractile ring thus preventing actin polymerization. how would this effect cell clevage and cytokinesis?

Back 20

If actin is unable to polymerize, the contractile ring can't form because it is made from actin microfilaments

Front 21

Blebbistain lowers the affinity of myosin motors for actin. how would this drug effect cytokinesis.

Back 21

if the myosin motors can't bind to the actin filaments, the contractile ring won't tighten and clevage won't occur.

Front 22

Describe the phases of apoptosis (3)

Back 22

1. chromosomes condense and cyoplasm shrinks
2.nuclues fragments, DNA is digested (laddering), cytoplasm becomes frgamented, cell extends blebs
3. remnants of dead cell are digessted by phagocytes.

Front 23

What role to capases play in apoptosis?

Back 23

capsases are producted as inactive procaspases which are cleaved to created the active enzyme. Once activated, they cleave other proteins within the cell

Front 24

What are the two ways apoptosis can be triggered?

Back 24

introduction of death signals or withdrawl of survival factors.

Front 25

Give two examples of "death signals"

Back 25

tumor necrosis factor and CD95.Fas

Front 26

The mitochondria can trigger apoptosis by releasing cytochrome C . How does cytochrome C trigger apopotsis? (2 ways)

Back 26

1. stimulate calcium release from the mitochonria and ER, the calcium inds to IP3
2. Activates procapase-9 into an apoptosome which makes active capase9, the executioner caspase

Front 27

How does the cytotoxic T lymphocyte trigger apoptosis

Back 27

It binds to the CD95 receptor on the target cell causing CD95 to aggregate in the infected cell. This results in the attachment of apaptor proteins which then recruits procaspase8. the procaspase becomes activated and initiatates the caspase cascade, eventually the executioner caspase.