Lecture 9 Flashcards

1
Q

Mitosis describs the process of ________ and cytokinesis describes the process of __________

A

Replicating and segregating the sets of chromosomes, cytokinesis is making the 1 cell into 2

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2
Q

Eukaryotic cell cycle 4 phases

A

-Growth phase (G1)
-Synthesis phase (S)
-Growth phase (G2)
-Mitotic (M)

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3
Q

In cytokinesis, where are actin and myosin highly concentrated

A

Contractile ring

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4
Q

What does the contractile ring do

A

Helps 2 cells pinch apart

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5
Q

Cytokinesis is the final step in cell division in which the _________ of a single eukaryotic cell is divided to form two daughter cells

A

Cytoplasm

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6
Q

First visible change in cytokinesis is the appearance of a

A

Cleavage furrow

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7
Q

What structure is responsibe for the contractile ring

A

Cleavage furrow

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8
Q

Contractile ring assembles beneath

A

Plasma membrane

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9
Q

Contractile ring pulls membrane _______

A

Inward

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10
Q

True or false: membrane vesicles fuse to PMAssembly of contractile ring

A
  1. Actin, tubulin and myosin disassemble in mother cell
  2. Monomeric actin and myosin accumulate at site of contractile ring (ANAPHASE)
  3. Local actin polymerizes- mediated in part by formin- establishing site of nucleation by unbranched actin
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11
Q

What happens as cleavage furrow deepens

A

Vesicles fuse to PM, surface area expansion

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12
Q

Adding taxol during cytokinesis

A

Prevents depolymerization of MTs, cant break apart asters, cell dies

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12
Q

Microtubules must _______ to facilitate formation of contractile ring

A

Depolymerize

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12
Q

The midbody contains

A

The central spindle, consisting of densly packed microtubules of the spindle midzone (actin-tubulin)

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13
Q

Disassembly of contractile ring

A
  1. During contraction, actin filaments depolymerize and exit ring to maintain size and volume
    2.Contractile ring is completely disassembled with formation of Midbody
  2. Midbody tethers daughter cells together (right before they seperate)
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14
Q

Local activation of RhoA triggers

A

Assembly and contraction of contractile ring

15
Q

Some things RhoA does:

A

-regulates remodelling of actin skeleton
-promotes actin polymerization
-binds and activates formin to promote actin nucleation at contractile ring
-Activates Rho Kinases (such as ROCK1)

16
Q

Rho in muscle contraction

A

Rho –> mDia (formin) –> profilin –> actin polymerization

17
Q

What ensures equal distribution of chromosomes

A

Spindles signal for furrow formation midway between 2 poles (anaphase)

18
Q

ER during cytokinesis

A

Segregates during interphase, also necessary for orientation of contractile ring

19
Q

Mitochondria during cytokinesis

A

Multiply prior to segregation, localize to cleavage furrow - likely to supply energy

20
Q

Golgi during cytokinesis

A

Fragments during M-phase in mammals, form cell plate in plants

21
Q

Asymmetrical division

A
22
Q

Positioning of cleavage furrow 3 mechanisms

A
  1. Astral stimulation model
  2. Central spindle model
  3. Astral relaxation model
23
Q

Astral stimulation

A

Signals being moved down the MTs toward the middle of the PM where furrow forms

24
Q

Central spindle stim model

A

Spindle mid zone (overlap) sends signals that transmit to cell cortex to activate Rho signalling pathway - formation of contractile ring

25
Q

Astral relaxation model

A

Relaxation of any contractile force where MTs meet PM - contractile force exerted only at cleavage furrow site