Trans - Cell Cycle and Apoptosis Flashcards
(97 cards)
1
Q
2 main jobs of the cell cycle
A
- to accurately transmit genetic information
2. to maintain normal ploidy
2
Q
aneuploidy - define
A
addition or subtraction of one or more single chromosomes (2n + 1, 2n - 1)
3
Q
euploidy - define
A
addition of whole chromosome sets (3n, 4n)
4
Q
interphase is __% of the cell cycle
A
95
5
Q
3 phases in interphase
A
G1, S, G2
6
Q
G1 - what happens?
A
organelle duplication but no DNA replication
7
Q
S - what happens?
A
semiconservative replication of DNA resulting in 2 identical daughter genomes
8
Q
G2 - what happens?
A
- Mitotic spindle begins to form
2. Cellular content further increases in preparation for M phase
9
Q
G0 - define
A
state of quiescence in nonproliferative cells, no cell division
10
Q
examples of cells that reach G0
A
muscle fibers, neurons
11
Q
examples of cells with fast or absent G1 phases
A
embryonic cells, stem cells, sperm cells
12
Q
G1 - number of chromsomes & chromatids, ploidy
A
46 chromosomes, 46 chromatids, 2n
13
Q
G2 - number of chromsoomes & chromatids, ploidy
A
46 chromosomes, 96 chromatids, 4n
14
Q
karyokinesis - define
A
separation of nuclei
15
Q
cytokinesis - define
A
separation of cytoplasm
16
Q
prophase - what happens?
A
chromatin condenses into chromosome structures
17
Q
prometaphase - what happens?
A
nuclear membrane disintegrates, kinetochores form
18
Q
metaphase - what happens?
A
condensed chromosomes line up in the middle of cells
19
Q
metaphase - what proteins are important in moving the chromsomes?
A
kinesin, dynein
20
Q
anaphase - what happens?
A
sister chromatids break up and are pulled to opposite poles
21
Q
telophase - what happens?
A
daughter nuclei are formed, chromosomes unravel, cytokinesis occurs
22
Q
4 prerequisites required for transmission of chromosomes
A
- one and only one centromere
2 functional telomeres at both ends - chromosomes must be fully replicated
- chromosomes cannot be too large or too small
23
Q
[T/F] cytokinesis is part of mitosis
A
F
24
Q
cytokinesis - how does this occur in animal cells?
A
cleavage furrow
25
cytokinesis - how does this occur in plant cells?
cell plate
26
[T/F] embryonic cells have no G1
T
27
3 cell cycle checkpoints
1. G1 checkpoint
2. G2 checkpoint
3. spindle assembly checkpoint
28
G1 checkpoint - what is it called in yeast? in animals?
Start in yeast
| Restriction (R) in animals
29
G1 checkpoint - what does it check for?
Checks for nutrient availability and cell size (cell won't divide if it is too small)
30
after which checkpoint is the cell committed to divide?
G1
31
G1 is sensitive to which signals?
growth factors
| TGF-beta
32
G2 checkpoint - what does it check for?
Checks for completion of DNA replication
33
G2 checkpoint - location
between G2 and M
34
spindle assembly checkpoint - location
between metaphase and anaphase
35
spindle assembly checkpoint - what does it check for?
All chromosomes must be properly attached to the spindle via TF4/kinetochore
36
spindle assembly checkpoint - what doe errors result into?
anaphase block / stopping of mitosis
37
spindle fibers - composition
alternating alpjha and beta tubulins, heterodimers
38
CDK - how does it exert its effects?
through phosphorylation of specific serine/threonine in protein substrates that perform various cell cycle events
39
how many CDK targets are there in humans? in xenopus?
humans - 292
| xenopus - 77
40
cyclin - function
regulation of CDK
41
cyclin - how does it regulate CDK?
binds to PSTAIRE a conserved motif in CDKs to form cyclin-CDK complexes
42
CDK - function
allows for cell cycle events to occur
43
what is the region of CDK that cyclin binds to
PSTAIRE
44
what is the region of cyclin that binds to CDK
five alpha helices making up the cyclin box
45
4 main cyclins in vertebrates
1. D
2. E
3. A
4. B
46
cyclin D - in what cell cycle stage does it bind CDK?
early to mid G1
47
cyclin D - function
cyclin-CDK complex inactivates pRB (cell cycle inhibitor)
48
cyclin E - in what cell cycle stage does it bind CDK?
G1 to S transition
49
cyclin E - function
promotes degradation of cyclin D
| promotes expression of cyclin A
50
cyclin A - in what cell cycle stage does it bind CDK?
G1 to S transition
51
cyclin A - function
regulator of cdc25 and CDK1, involved in activating cyclin B/CDK1 complex
52
cyclin B - in what cell cycle stage does it bind CDK?
entry to M phase
53
cyclin B - function
binds CDK1 to make MPF (mitosis promoting factor)
54
cyclin levels generally increase in (1)__ or (2)___, but never in (3)___
1. G1
2. S
3. G2
55
3 ways of CDK regulation
1. cyclin synthesis and destruction
2. CDK phosphorylation
3. binding to inhibitors
56
how is cyclin destruction controlled
through polyubiquitination of mitotic cyclin
57
wee1 - function
inhibitor of cyclin-CDK complex formation via steric blocking
58
cdc25 - function
activator of cyclin-CDK complex formation
59
deficit of cdc25, excess wee1 - consequences
elongated cells (increased G2)
60
deficit of wee1, excess cdc25 - consequences
smaller cells (decreased G2)
61
T-loop - function
blocks substrate binding site in free CDK
62
t161 phosphorylation - significance
moves t-loop away from substrate binding site, allowing formation of CDK-cyclin complex
63
p21 family - function, mechanism
inhibitor of CDK, through binding to the active stie
64
INK4 family - function, mechanism
inhibitor of CDK, inhibits by replacing cyclin
65
inhibitors of CDK - what stage in the cell cycle do they regulate?
G1 to S transition
66
most mutated CDK inhibitor in humans
p16
67
proto-oncogenes - define
genes that promote normal cell division
68
oncogenes - define
genes that cause cancer, mutated proto-oncogenes
69
tumor supporessor genes - define
genes that prevent cells from dividing
70
car brake analogy of cancer - 1st mutation
active oncogenes + tumor suppressor gene = susceptible carrier
71
car brake analogy of cancer - 2nd mutation
active oncogenes + mutation in tumor suppressor genes = cancer symptoms
72
two hit hypothesis of cancer
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
P53 tumor suppressor protein - significance
triggers apoptosis in tumor cells through excessive DNA damage
74
apoptosis - definition
programmed or physiological cell death
75
what is the difference between the growth of unicellular and multicellular organisms?
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
mitogens - function
allow cell to enter mitosis
77
growth factors - function
increase cell mass
78
survival factors - function
suppress apoptosis
79
cell death by suicide - types of signals
internal and external
80
cell death by suicide - internal signals
triggered from within the cells in response to developmental cues or severe cell stress
81
cell death by suicide - external signals
activated by pro-apoptotic ligands binding to pro-apoptotic death receptors
82
apoptosis - why
1. for proper development (e.g. interphalangeal webs)
| 2. to destroy infected cells
83
what makes a cell decide to commit suicide?
1. removal of positive signals
| 2. receipt of negative signals
84
signals that prevent apoptosis
1. growth factors
| 2. IL 2
85
signals that promote apoptosis
1. increased levels of oxidants within the cells
2. damage to DNA
3. death activators
86
death activators - examples
1. tumor necrosis factor alpha (TNF-alpha)
2. lymphotoxin (TNF-beta)
3. Fas ligand (FasL)
87
6 general features of apoptosis
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
cytochrome C - significance
release of cytochrome C from mitochrondria initiates apoptotic mechanism
89
number of cells that die each day in adult? in child?
adult - 50-70 billion cells
| child - 20-30 billion cells
90
progression of appearance of apoptotic cell in culture
normal cell --> blebs --> spikes --> blisters
91
karyolysis - define
nuclear fading - chromatin dissolution due to action of DNAses and RNAses
92
pyknosis - define
nuclear shrinkage - DNA condenses into shrunken basophilic mass
93
karyorrhexis - define
nuclear fragmentation - pyknotic nuclear membrane ruptures and undergoes fragmentation
94
caspases - define
proteins that degrade other proteins
95
inactive form of caspases
procaspases
96
4 examples of virus proteins that can inhibit caspases
1. CrmA
2. Baculovirusp35
3. Ebstein Barr virus BHRFI protein
4. Ebstein Barr virus LMP-1 protein
97
effect of caspase inhibition
inhibition of apoptosis - uncontrolled cell division
