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Advanced Cells > lec 6-7 cell cycle and cell polarity > Flashcards

lec 6-7 cell cycle and cell polarity Flashcards

1
Q

defects in cell division

A

lead to chromosome abnormalities

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2
Q

when is the genome replicated (eukaryotic)

A

S phase

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3
Q

what is the order of the cell cycle

A

G1
S
G2
M

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4
Q

G1

A

commitment to cell division

cell grows in size
synthesises mRNA and proteins (histones) required for DNA synthesis

checkpoint before S phase

  • formation of G1/S cyclin with Cdk
  • is environment suitable e.g. pH
  • integrity of DNA assessed
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5
Q

if a cell does not clear to pass through to S phase..

A

enters G0, dormant phase

- no cell growth or division

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6
Q

G2

A

rapid cell growth and protein synthesis

preparation for mitosis

checkpoint:
G2/M
- checks for damage

if damage signals activate p53
Cdk1 inhibited
cell cycle does not progress

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7
Q

hartwell discovered

A

checkpoints using budding yeast

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8
Q

paul nurse discovered

A

cdk and regulators using fission yeast

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9
Q

hunt discovered

A

cyclins using sea urchins

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10
Q

Wee1

A

kinase
influences cell size
inhibits entry of cell cycle into mitosis
inhibits cdk1 by phosphorylation

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11
Q

proteolysis

A

degradation of a protein

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12
Q

mitosis

A

segregation of equal numbers of chromosomes into each daughter cell

2 genetically identical daughter cells

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13
Q

outline steps of mitosis

A 
DNA condenses
centrosome duplicates
microtubules terminate and attach to chromosomes
chromosomes align on mitotic spindle 
separate to opposite ends
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14
Q

3 types of microtbule making up mitotic spindle

A

astral
interpolar
kinetochore

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15
Q

astral microtubules

A

anchor the spindle poles to the cell membrane

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16
Q

interpolar microtubules

A

overlap/interlock and the spindle midzone

keep poles at correct distance apart

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17
Q

kinetochore microtubules

A

mediate attachment of kinetochore microtubules to chromosome via kinetochore complex (attachment site)

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18
Q

chromosome movement

A

microtubule polymerisation

kinetochore microtubules shorten and draw chromosomes towards spindle poles

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19
Q

role of microtubules in cytokinesis

A

position plane of division

contractile ring drives cleavage (actin and myosin motor protein also involved)

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20
Q

s phase

A

DNA replication

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21
Q

M phase

A

mitosis - nuclear division
cytokinesis - cytoplasmic division

checkpoint 3 - are all chromosomes properly attached to mitotic spindle?

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22
Q

activation of cdk

A

activated by cyclins

cyclin concentration oscillates during cell cycle

causes cell cycle to progress

23
Q

cdc2

A

cell division cycle protein 2 - same as cdk1

24
Q

negative regulator of cell division

A

Wee1 - kinase

25
Q

Cdc25

A

phosphotase
positive regulator of cell division
stimulates cdc2/cdk1
progression of cell cycle

26
Q

ndc80

A

protein ring complex
attaches to kinetochore and microtubule
leaves space in between for microtubule polymerisation

27
Q

amphitelic attachment

A
  • Each kinetochore is attached to microtubules from opposing spindle poles
  • monomers of intermediate filaments interact in both parallel and anti-parallel manners to form dimers
28
Q

syntelic attachment

A
  • Both sister kinetochores are attached to MTs from the same spindle pole
29
Q

monotelic

A
  • One kinetochore is attached to a MT from a spindle pole and the other kinetochore is not attached to a MT
30
Q

spindle assembly checkpoint - SAC

A

in M phase

checks all microtubules are properly attached to the spindle

31
Q

polarity

A

having one end morphologically/funcionally different from the other

32
Q

why is polarity necessary

A

cellular morphogenesis
tissue morphogenesis
organism morphogenesis

33
Q

4 main examples of polarisation mechanisms

A

neuronal guidance
assymetrical cell division
yeast mating
cell migration

34
Q

how is cell polarity acheived

A

cytoskeletal remodelling
signal pathways converge on actin and microtubule cytoskeletons
reassembly of filaments at new sites

35
Q

taxis

A

motion of orientation of a cell/organism in response to an external stimulus

36
Q

GEFs

A

proteins that activate GTPases by stimulating release of GDP

37
Q

GDIs

A

bind to GDP-bound GTPases and prevent exchange

38
Q

guidance cue

A

something that attracts or repels the cell
either contact/adhesion or chemical
recognised by receptors on growth cones (structure at tip)

39
Q

contact/adhesion guidance cues

A

proteins form a substrate on which the cell can crawl
ECM
often short-range

e.g. cadherins attract

40
Q

chemical guidance cues

A

secreted

often long-range

e.g. netrins attract, semaphorins repel

41
Q

commissural neurons

A

use guidance cues to project onto the other side of the CNS

ensure left-right synchronisation

42
Q

DDC receptors for netrin

A

once activated, lead to signal cascade

growth cones crawls in direction of ventral midline in brain

43
Q

slit protein

A

has opposite effect to netrin, prevents neurons crossing midline again

secreted by floor plate

44
Q

role of GPCR

A

to transduce an extracellular signal to a small GTPase to cause a cellular response

45
Q

examples of small monomeric GTPases

A

Rho

Ras

46
Q

substrate level phosphorylation

A

metabolic process

results in ATP/GTP formation by direct transfer of a phosphate group

47
Q

central regulator or cell polarity

A

cdc42

48
Q

par proteins

A

responsible for asymmetric positioning of mitotic spindle
help polarise tissues

relocalise over time

e.g. LBK1 is a human par protein

49
Q

epithelial apical-based polarity

A

plasma membrane of epithelial cells is divided into two domains
splits top and bottom

50
Q

what separates apex and baso-lateral surface

A

tight junctions

51
Q

apical surface

A

permeable to water-soluble molecules
surface area can be increased
faces externally

52
Q

basolateral surface

A

impermeable
faces internally
in contact with blood supply

53
Q

2 complexes associated with par proteins

A

scribble and crumbs

54
Q

role of par proteins

A

kinases - switch other proteins on/off

scaffolding factors interact and recruit other proteins

Advanced Cells (10 decks)

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