Cell Cycle Control & Cell Division Part I (Exam IV) Flashcards
1
Q
The cell cycle involves what two phases in order to create two identical daughter cells:
A
- Replication phase
- Division phase
2
Q
What triggers the major events of the cell cycle
A
Cell-cycle control system
3
Q
As the cell cycle proceeds, a series of ______ ensure that each phase is complete before the next one begins
A
Checkpoints
4
Q
How many many major checkpoints are in the eukaryotic cell cycle
A
Three
5
Q
What control cell proliferation
A
Cell-cycle control machinery
6
Q
Inappropriate cell proliferation
A
Cancer
7
Q
Many of the genes (proteins) involved in the cell-cycle regulation are critical determinants of:
A
Cancer progression
8
Q
G1 & G2 are the ____ phases of the cell cycle
A
Gap phases
9
Q
Phase of the cell cycle in which DNA synthesis takes place
A
S phase
10
Q
Phase of the cell cycle in which division takes place
A
M phase
11
Q
The three important check points occur during:
A
late G1 checkpoint
G2/M checkpoint
metaphase to anaphase transition checkpoint
12
Q
Checkpoint in late G1 checks for:
A
if the environment is favorable for cell division
13
Q
In the late G1 checkpoint what is being checked in the environment to insure favorable conditions:
A
Hormone signals, nutrients, etc.
14
Q
The G2/M check points is assessing whether:
A
Correct replication of DNA
Favorable environment
15
Q
If at the G2/M checkpoint the cell determines it can go on, it will enter the:
A
M phase
16
Q
The cell won’t separate the chromosome & split without the go ahead from the:
A
Metaphase to anaphase transition checkpoint
17
Q
Checkpoint that asks:
Is the environment favorable
A
Late G1 checkpoint (start checkpoint)
18
Q
Checkpoint that asks:
Is all the DNA replicated
Is the environment favorable
A
G2/M checkpoint
19
Q
Checkpoint that asks:
Are all the chromosomes attached to the spindle
A
Metaphase to anaphase transition checkpoint
20
Q
After the G1/S checkpoint the cell proceeds to:
After the G2M checkpoint, the cell proceeds to:
After the metaphase to anaphase transition checkpoint, the cell proceeds to:
A
Enters the cell cycle and proceeds to S phase
Enters mitosis
Triggers anaphase & proceeds to cytokinesis
21
Q
The cell-cycle checkpoint control system depends on:
A
1- Cyclically activated cyclin-dependent protein kinases (Cdks)
2- Cyclical proteolytic events
3- transcriptional regulation
22
Q
Triggers the events that occur in each phase of the cell cycle:
A
Cell-cycle control system
23
Q
The cell-cycle control system insures the proper _____, _____ & _____ of the events
A
Timing, order & fidelity
24
Q
Type of signals the cell-cycle control system responds to:
A
Intracellular & extracellular signals
25
Whenever the cell fails to complete an essential cell-cycle process or encounters unfavorable intracellular or extracellular conditions, the cell-cycle control system:
Arrests
26
Important critical determinants to the mammalian cell cycle:
Cyclin-dependent kinases (Cyclin-Cdks)
27
Where the cell gets pulled out of the normal cell cycle & is put into a quiescent state:
G0 phase
28
Cyclins & cyclin-dependent kinases are critical determinants for the transition of:
One cell cycle phase to the next
29
For the cyclin-dependent kinases to become activated what first must occur:
binding of the specific cyclin that recognizes that CDK to create a complex
30
Following the binding of the specific cyclin to the CDK, creating a complex, what takes place:
Subsequent specific phosphorylations
31
The specific phosphorylations that take place on the cyclin-CDK complex turn this complex into a:
Activated state
32
If the cyclin is not present, the CDK will be:
Inactive
33
The initial checkpoint that occurs in late G1 involves what cyclin:
G1/S-cyclin pair
34
The G1/S-cyclin pair comes up and reaches a peak in _____ & then the as the cell moves from G1 to S this cyclin:
Late G1
Falls off
35
The S-cyclin is necessary for the start of:
Synthesis
36
As the G1/S-cyclin is falling off, the S-cyclin:
Begins to work
37
As we reach into the mitosis phase the S-cyclin ____ and the M-cyclin has reached a _____
Falls off
Critical level
38
When does the M-cyclin level decrease:
Metaphase to anaphase transition
39
The cyclin molecules ______ in their concentration because they are ______
Oscillate; induced
40
Has the enzymatic activity in the cell cycle
CDKs
41
The concentrations of the three major cyclin proteins oscillate during the cell cycle; their express is _____ to promote transitions through the cell cycle
Induced
42
The concentrations of the Cdk do not change because they are:
Constitutively expressed
43
Critical for determining transitions from one phase of the cell-cycle to the next
appearance/disappearance of cyclins
44
In addition the specific necessary cyclin, the _______ or _____ initiates the metaphase to anaphase transition
Anaphase-promoting complex or cyclosome (APC/C)
45
There are three D cyclins in mammals including:
Cyclins D1, D2 & D3
46
During the cell-cycle processs, the CDKs are constitutively expressed in an:
Inactive state
47
CDKs only become activate if the:
Proper cyclin molecule is expressed
48
Why are the CDKs originally inactive:
Due to active site being blocked by T-loop
49
What molecule is the T-loop covering & on
CDK
50
The presence of the T-loop (folded over the active site) prevents it from:
Phosphorylating
51
When the cyclin binds to the CDK this causes the T-loop to:
Change its configuration
52
When the T-loop changes its configuration due to the binding of the cyclin this results in:
A partially activated CDK
53
In order for the CDK to become fully activated, there is an enzyme called ____ that comes in and phosphorylates the T-loop
CDK-activating-kinase (CAK)
54
The CAK is responsible for:
Phosphorylating the T-loop
55
Where does the CAK phosphorylate the T-loop:
Very specific threonine
56
When the threonine in of the T-loop is phosphorylated by the CAK this results in:
Fully activated CDK
57
List the basic steps of the activation of CDK
1- Cyclin binds
2- T-loop moves
3- CAK phosphorylates
4- fully active CDK molecule
58
Each cyclin partner is important for determining which specific targets are subsequently:
Phosphorylated by the CDK subunit
59
Each cyclin-CDK can induce different effects at different times in the cell-cycle based upon the relative:
Presence, absence or abundance of each specific target
60
Activation of the cyclin-CDK complex is a prerequisite for:
Downstream events
61
The activity of each cyclin-CDK complex is finely regulated by:
Additional mechanisms
62
Just as mutations that alter cyclin or CDK function can lead to misregulation of the cell cycle, so too can mutations that disrupt any of these regulatory mechanisms creat the possible that a:
Cancer of some type may occur
63
The fine-tuning of the activation of the cyclin-CDK is controlled by the two enzymes:
Wee1-kinase
Cdc25-phosphatase
64
Phosphorylates a second site on the CDK molecule rendering it inactive
Wee1-kinase
65
What enzyme is opposed by Cdc25-phosphatase:
Wee1-kinase
66
Removes the inhibitory phosphate, putting the cyclin-CDK back into an active state:
Cdc25-phosphatase
67
The Wee1-kinase and the Cdc25-phosphatase give a ____ level of regulation
rapid
68
Two groups of proteins that are really important to the cell-cycle with respect to proteolysis:
APC/C
SCF
69
APC/C is a member of the:
Ubiquitin ligase family of proteins
70
Anytime ubiquitin molecules get added to a protein, this flags it for:
Degredation
71
APC/C is important in degradation of:
Securin & S- & M-cyclins
72
Securin is involved in protecting the _____ that hold the _____ together
Protein linkages; sister chromatids
73
Securin degradation leads to the activation of a _____ that then separates the sisters & unleashes:
Protease
Anaphase
74
Degradation of the s- & m-cyclins leads to inactivation of the:
Cdks
75
Loss of the Cdks means that their targets can be _____ by various _____ present in anaphase
Dephosphorylated
Phosphates
76
The loss of the Cdks & dephosphorylation of their targets by various phosphatase that are present in anaphase completes the:
M phase
77
APC/C is activated in ______ & remains active in ____
Mid-mitosis; G1
78
APC/C is activated in mid-mitosis & remains active in G1 which provides a period in which:
Cdk is inactive
79
When the G1/S-Cdks are activated in late G1 ______ is turned off
APC/C
80
When the G1/S-Cdks are activated in late G1, APC/C is turned off allowing for:
Cyclin accumulation to start the next cell cycle
81
APC/C activity changes during the cell cycle due to its interactions with _____ in anaphase & ____ from late mitosis through early G1
Cdc20
Cdh1
82
Ubiquination leads to degredation by the:
Proteosome complex
83
SCF is a:
Ubiquitin ligase
84
SCF is comprised of what subunits:
S, C, F subunits
85
SCF ubiquitylates:
Cdk inhibitor proteins (CKI)
86
SCF ubiquitylates CDK inhibitor proteins in:
Late G1
87
A common Cdk inhibitor protein:
P27
88
The ubiquination of the Cdk inhibitor proteins allows the cell to transition from ____ to ____ as the G1/S-Cyclin comes up
G1 to S phase
89
P27 _______ the active cyclin-Cdk complex
Inhibits
90
One portion of the p27 Cdk inhibitor protein binds to ____ while the other portion binds to ____ of the cyclin-Cdk complex
Cdk portion; cyclin portion
91
Where the p27 binds to the Cdk protein this occurs specifically at the:
Active site of the Cdk
92
The p27 inactivation of the cyclin-Cdk complex is very:
Stable
93
The most important subunit of the active SCF complex is the:
F-box protein
94
The F-box proteins recognize the ______ when those proteins become phosphorylated
Cdk-inhibitory proteins
95
When the F-box protein recognizes the phosphorylated CKI, this causes the CKI to get:
Ubiquinated
96
The F-box recognizing the CKI resulting in ubiquination of the CKI ultimately results in its:
Degradation
97
You have fine level regulation of the cyclin-Cdk complex by:
You can also physically remove the inhibitor proteins present by:
Phosphorylation-Dephosphorylation reactions
Ubiquitination processes by APC/C or SCF
98
Cyclin genes are:
Inducible
99
When the cyclin genes get induced at the correct time, the cell-cycle:
Will move into the next phase
100
Phosphorylates the activating site in Cdks:
Cdk-activating kinase (CAK)
101
Phosphorylates inhibitory sites in Cdks; primarily involved in suppressing Cdk1 activity before mitosis:
Wee1-kinase
102
Removes inhibitory phosphates from Cdks; three family members (A, B, C) in mammals; primarily involved in controlling Cdk1 activation at the onset of mitosis:
Cdc25-phosphatase
103
Common Cdk-inhibitor proteins (CKIs):
Sic1
P27
P21
P16
104
Catalyzes ubiquitylation of regulatory proteins involved primarily in exit of mitosis, including securin and s- & m-cyclones; regulated by association with activating subunits:
APC/C
105
APC/C-activating subunit in all cells; triggers initial activation of APC/C at metaphase-to-anaphase transition; stimulated by m-Cdk activity:
Cdc20
106
APC/C-activating subunit that maintains APC/C activity after anaphase & throughout G1; inhibited by Cdk activity:
Cdh1
107
Catalyzes ubiquitylation of regulatory proteins in G1 control, including some CKIs; phosphorylation of target protein, usually required for activity:
SCF
108
A Cdk-inhibitor protein (CKI) that suppresses G1/S-Cdk & s-Cdk activities in G1; helps cells withdraw from the cell cycle when they terminally differentiate; phosphorylation by Cdk2 triggers its ubiquitylation by SCF:
P27
109
The central component of the control system is the series of ____ that regulate transitions through the various phases
Cyclin-Cdk complexes
110
The cyclin-Cdk complexes are also regulated by various ____ which provide information about the extracellular environment, DNA, or cell damage & whether each step in the cell-cycle has been properly completed
Inhibitory mechanisms
111
In cancers a lot of the cell-cycle control mechanisms are:
Over-ridden
112
G0 represents a:
Resting or quiescent state
113
Cells can remain in G0 phase for:
Days to weeks or longer before resuming proliferation
114
Cells can enter G0 phase:
Permanently until they die
115
Cells enter G0 from a cell-cycle checkpoint in:
The G1 phase
116
G0 entry usually occurs due to:
Lack of growth factors or nutrients
117
G0 also occurs in cells when they reach:
Maturity
118
An example of maturity of a cell that enter G0 could be when the cell becomes:
Terminally differentiated
119
Examples of terminally differentiated cells:
Nerve cells
Heart muscle cells
Bone osteocytes
120
The dREAM complex forms & leads to _____ which leads to ____
Histone compaction; suppression of gene expression
121
The dREAM complex puts cells into a dream state where they sit there and do nothing but:
Metabolize
122
The dREAM complex binds exclusively to:
Deacetylated histone H4
123
The dREAM complex is induced by _____ resulting in the compaction of DNA in those regions
Histone modification
124
The dREAM complex moves genes from a ______ state to a ______ state
Euchromatin to heterochromatin
125
Protein (enzyme) that phosphorylates a target protein or another molecule:
Kinase
126
Protein (enzyme) that removes a phosphate moiety from a protein or another molecule:
Phosphatase
127
Family of protein-kinases involved in control of the cell-cycle:
Cyclin-dependent kinases (Cdks)
128
Family of proteins that regulate Cdk activity:
Cyclins
129
Regulatory transitions in the cell-cycle in which the cell cycle will be arrested unless specific prior biochemical events are fully completed:
Checkpoints
130
Cell-division-cycle genes; important in cell-cycle checkpoint control:
Cdc
131
Cdk-activating kinase:
CAK
132
Anaphase promoting complex or cyclosome:
APC/C
133
Cdk inhibitor protein:
CKI
134
Ubiquitin ligase involved in cell-cycle control; named after its three subunits:
SCF
135
Origin recognition complex: protein complex bound to origin of replication sites in DNA:
ORC
136
Complex of proteins involved in the cell cycle control arrest & senescence by binding to the E2F family of transcription factors:
DREAM
137
Retinoblastoma protein: involved in cell cycle regulation:
Rb
138
Genes that turn on & off dependent upon cues from environment, hormones, etc. that need to be present in the cell:
Inducible gene expression
139
Genes that are expressed at a constant level throughout the life of the cell:
Constitutive gene expression
