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[OS 201] 4th Exam > Trans - Cell Cycle and Apoptosis > Flashcards

Trans - Cell Cycle and Apoptosis Flashcards

1
Q

2 main jobs of the cell cycle

A
  1. to accurately transmit genetic information

2. to maintain normal ploidy

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2
Q

aneuploidy - define

A

addition or subtraction of one or more single chromosomes (2n + 1, 2n - 1)

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3
Q

euploidy - define

A

addition of whole chromosome sets (3n, 4n)

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4
Q

interphase is __% of the cell cycle

A

95

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5
Q

3 phases in interphase

A

G1, S, G2

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6
Q

G1 - what happens?

A

organelle duplication but no DNA replication

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7
Q

S - what happens?

A

semiconservative replication of DNA resulting in 2 identical daughter genomes

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8
Q

G2 - what happens?

A
  1. Mitotic spindle begins to form

2. Cellular content further increases in preparation for M phase

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9
Q

G0 - define

A

state of quiescence in nonproliferative cells, no cell division

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10
Q

examples of cells that reach G0

A

muscle fibers, neurons

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11
Q

examples of cells with fast or absent G1 phases

A

embryonic cells, stem cells, sperm cells

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12
Q

G1 - number of chromsomes & chromatids, ploidy

A

46 chromosomes, 46 chromatids, 2n

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13
Q

G2 - number of chromsoomes & chromatids, ploidy

A

46 chromosomes, 96 chromatids, 4n

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14
Q

karyokinesis - define

A

separation of nuclei

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15
Q

cytokinesis - define

A

separation of cytoplasm

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16
Q

prophase - what happens?

A

chromatin condenses into chromosome structures

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17
Q

prometaphase - what happens?

A

nuclear membrane disintegrates, kinetochores form

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18
Q

metaphase - what happens?

A

condensed chromosomes line up in the middle of cells

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19
Q

metaphase - what proteins are important in moving the chromsomes?

A

kinesin, dynein

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20
Q

anaphase - what happens?

A

sister chromatids break up and are pulled to opposite poles

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21
Q

telophase - what happens?

A

daughter nuclei are formed, chromosomes unravel, cytokinesis occurs

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22
Q

4 prerequisites required for transmission of chromosomes

A
  1. one and only one centromere
    2 functional telomeres at both ends
  2. chromosomes must be fully replicated
  3. chromosomes cannot be too large or too small
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23
Q

[T/F] cytokinesis is part of mitosis

A

F

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24
Q

cytokinesis - how does this occur in animal cells?

A

cleavage furrow

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25
Q

cytokinesis - how does this occur in plant cells?

A

cell plate

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26
Q

[T/F] embryonic cells have no G1

A

T

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27
Q

3 cell cycle checkpoints

A
  1. G1 checkpoint
  2. G2 checkpoint
  3. spindle assembly checkpoint
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28
Q

G1 checkpoint - what is it called in yeast? in animals?

A

Start in yeast

Restriction (R) in animals

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29
Q

G1 checkpoint - what does it check for?

A

Checks for nutrient availability and cell size (cell won’t divide if it is too small)

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30
Q

after which checkpoint is the cell committed to divide?

A

G1

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31
Q

G1 is sensitive to which signals?

A

growth factors

TGF-beta

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32
Q

G2 checkpoint - what does it check for?

A

Checks for completion of DNA replication

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33
Q

G2 checkpoint - location

A

between G2 and M

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34
Q

spindle assembly checkpoint - location

A

between metaphase and anaphase

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35
Q

spindle assembly checkpoint - what does it check for?

A

All chromosomes must be properly attached to the spindle via TF4/kinetochore

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36
Q

spindle assembly checkpoint - what doe errors result into?

A

anaphase block / stopping of mitosis

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37
Q

spindle fibers - composition

A

alternating alpjha and beta tubulins, heterodimers

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38
Q

CDK - how does it exert its effects?

A

through phosphorylation of specific serine/threonine in protein substrates that perform various cell cycle events

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39
Q

how many CDK targets are there in humans? in xenopus?

A

humans - 292

xenopus - 77

40
Q

cyclin - function

A

regulation of CDK

41
Q

cyclin - how does it regulate CDK?

A

binds to PSTAIRE a conserved motif in CDKs to form cyclin-CDK complexes

42
Q

CDK - function

A

allows for cell cycle events to occur

43
Q

what is the region of CDK that cyclin binds to

A

PSTAIRE

44
Q

what is the region of cyclin that binds to CDK

A

five alpha helices making up the cyclin box

45
Q

4 main cyclins in vertebrates

A
  1. D
  2. E
  3. A
  4. B
46
Q

cyclin D - in what cell cycle stage does it bind CDK?

A

early to mid G1

47
Q

cyclin D - function

A

cyclin-CDK complex inactivates pRB (cell cycle inhibitor)

48
Q

cyclin E - in what cell cycle stage does it bind CDK?

A

G1 to S transition

49
Q

cyclin E - function

A

promotes degradation of cyclin D

promotes expression of cyclin A

50
Q

cyclin A - in what cell cycle stage does it bind CDK?

A

G1 to S transition

51
Q

cyclin A - function

A

regulator of cdc25 and CDK1, involved in activating cyclin B/CDK1 complex

52
Q

cyclin B - in what cell cycle stage does it bind CDK?

A

entry to M phase

53
Q

cyclin B - function

A

binds CDK1 to make MPF (mitosis promoting factor)

54
Q

cyclin levels generally increase in (1)__ or (2)___, but never in (3)___

A
  1. G1
  2. S
  3. G2
55
Q

3 ways of CDK regulation

A
  1. cyclin synthesis and destruction
  2. CDK phosphorylation
  3. binding to inhibitors
56
Q

how is cyclin destruction controlled

A

through polyubiquitination of mitotic cyclin

57
Q

wee1 - function

A

inhibitor of cyclin-CDK complex formation via steric blocking

58
Q

cdc25 - function

A

activator of cyclin-CDK complex formation

59
Q

deficit of cdc25, excess wee1 - consequences

A

elongated cells (increased G2)

60
Q

deficit of wee1, excess cdc25 - consequences

A

smaller cells (decreased G2)

61
Q

T-loop - function

A

blocks substrate binding site in free CDK

62
Q

t161 phosphorylation - significance

A

moves t-loop away from substrate binding site, allowing formation of CDK-cyclin complex

63
Q

p21 family - function, mechanism

A

inhibitor of CDK, through binding to the active stie

64
Q

INK4 family - function, mechanism

A

inhibitor of CDK, inhibits by replacing cyclin

65
Q

inhibitors of CDK - what stage in the cell cycle do they regulate?

A

G1 to S transition

66
Q

most mutated CDK inhibitor in humans

A

p16

67
Q

proto-oncogenes - define

A

genes that promote normal cell division

68
Q

oncogenes - define

A

genes that cause cancer, mutated proto-oncogenes

69
Q

tumor supporessor genes - define

A

genes that prevent cells from dividing

70
Q

car brake analogy of cancer - 1st mutation

A

active oncogenes + tumor suppressor gene = susceptible carrier

71
Q

car brake analogy of cancer - 2nd mutation

A

active oncogenes + mutation in tumor suppressor genes = cancer symptoms

72
Q

two hit hypothesis of cancer

A
  1. if somatic mutations hit first, cancer is unlikely/localized
  2. if germline mutations hit first, cancer is likely to form all across the body
73
Q

P53 tumor suppressor protein - significance

A

triggers apoptosis in tumor cells through excessive DNA damage

74
Q

apoptosis - definition

A

programmed or physiological cell death

75
Q

what is the difference between the growth of unicellular and multicellular organisms?

A

unicellular organisms depend solely on the amount of nutrients in the environment for rate of growth, multicellular organisms have various regulatory mechanisms to control growth

76
Q

mitogens - function

A

allow cell to enter mitosis

77
Q

growth factors - function

A

increase cell mass

78
Q

survival factors - function

A

suppress apoptosis

79
Q

cell death by suicide - types of signals

A

internal and external

80
Q

cell death by suicide - internal signals

A

triggered from within the cells in response to developmental cues or severe cell stress

81
Q

cell death by suicide - external signals

A

activated by pro-apoptotic ligands binding to pro-apoptotic death receptors

82
Q

apoptosis - why

A
  1. for proper development (e.g. interphalangeal webs)

2. to destroy infected cells

83
Q

what makes a cell decide to commit suicide?

A
  1. removal of positive signals

2. receipt of negative signals

84
Q

signals that prevent apoptosis

A
  1. growth factors

2. IL 2

85
Q

signals that promote apoptosis

A
  1. increased levels of oxidants within the cells
  2. damage to DNA
  3. death activators
86
Q

death activators - examples

A
  1. tumor necrosis factor alpha (TNF-alpha)
  2. lymphotoxin (TNF-beta)
  3. Fas ligand (FasL)
87
Q

6 general features of apoptosis

A
  1. many activities take place within the cell
  2. translocation of phosphatidylserine to outer membrane
  3. ATP dependency
  4. internucleosomal DNA fragmentation
  5. no apoptosis at +4C
  6. no inflammation
88
Q

cytochrome C - significance

A

release of cytochrome C from mitochrondria initiates apoptotic mechanism

89
Q

number of cells that die each day in adult? in child?

A

adult - 50-70 billion cells

child - 20-30 billion cells

90
Q

progression of appearance of apoptotic cell in culture

A

normal cell –> blebs –> spikes –> blisters

91
Q

karyolysis - define

A

nuclear fading - chromatin dissolution due to action of DNAses and RNAses

92
Q

pyknosis - define

A

nuclear shrinkage - DNA condenses into shrunken basophilic mass

93
Q

karyorrhexis - define

A

nuclear fragmentation - pyknotic nuclear membrane ruptures and undergoes fragmentation

94
Q

caspases - define

A

proteins that degrade other proteins

95
Q

inactive form of caspases

A

procaspases

96
Q

4 examples of virus proteins that can inhibit caspases

A
  1. CrmA
  2. Baculovirusp35
  3. Ebstein Barr virus BHRFI protein
  4. Ebstein Barr virus LMP-1 protein
97
Q

effect of caspase inhibition

A

inhibition of apoptosis - uncontrolled cell division

[OS 201] 4th Exam (5 decks)

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