Cell Cycle Control and Cell Division

Question 1

The cell-cycle involves DNA replication and dividing the cell to
create

Answer 1

two identical daughter cells

Question 2

The cell-cycle control system triggers the major events of the

Answer 2

cell cycle

Question 3

As the cell cycle proceeds a series of (2) ensure

that each phase is complete before the next one begins

Answer 3

transitions or checkpoints

Question 4

There are - major checkpoints in eukaryotic cells

Answer 4

3

Question 5

The cell-cycle control machinery therefore controls

Answer 5

cell proliferation

Question 6

— is essentially inappropriate proliferation

Answer 6

Cancer

Question 7

Many of the genes (proteins) involved in cell-cycle regulation are
critical determinants of

Answer 7

cancer progression

Question 8

The system depends on cyclically activated

Answer 8

cyclin-dependent protein kinases (Cdks)

Question 9

The cell-cycle control system depends on

Answer 9

cyclical proteolytic events

Question 10

The cell-cycle control depends on

Answer 10

transcriptional regulation

Question 11

The Cell-Cycle Control System triggers the events that occur in each phase of
the

Answer 11

cell cycle

Question 12

The Cell-Cycle Control System ensures the proper (3)

Answer 12

timing, order and fidelity of

the events

Question 13

The Cell-Cycle Control System responds to (2)

Answer 13

intracellular and extracellular signals

Question 14

The Cell-Cycle Control System arrests the cycle whenever the cell (2)

Answer 14

fails to
complete an essential cell-cycle process or
encounters unfavorable intracellular or
extracellular conditions

Question 15

Control of the Cell-cycle by (2)

Answer 15

Cyclins and Cyclin-Dependent Protein Kinases (Cdks)

Question 16

Cyclin-dependent kinase (Cdk) requires the binding of — and subsequent specific — to become an active enzyme

Answer 16

cyclin

phosphorylation

Question 17

In the absence of cyclin, Cdk is in an — state

Answer 17

inactive

Question 18

The concentrations of the three major cyclin proteins

— during the cell cycle

Answer 18

oscillate

Question 19

their expression is —

to promote transitions through the cell cycle

Answer 19

induced

Question 20

The concentrations of the Cdk…

Answer 20

do not change

Question 21

constitutive expression

Answer 21

concentration do not change

Question 22

The appearance and disappearance of the various cyclins

are critical for determining the

Answer 22

transitions from one phase

of the cell-cycle to the next

Question 23

in addition, the Anaphase-Promoting Complex or

Cyclosome (APC/C) initiates the

Answer 23

metaphase to anaphase

transition

Question 24

G1-Cdk cyclin

Answer 24

D

Question 25

G1/S-Cdk cyclin

Answer 25

E

Question 26

S-Cdk cyclin

Answer 26

A

Question 27

M-Cdk cyclin

Answer 27

B

Question 28

In the inactive state the catalytic or active site of the cyclin-dependent
kinase is blocked by the presence of a region called the

Answer 28

T-loop

Question 29

Binding

of the specific cyclin to its cognate cyclin-dependent kinase leads to

Answer 29

a
movement of the T-loop away from the active site, leading to partial
activation

Question 30

Cdk-activating kinase (CAK) can then

Answer 30

phosphorylate the T-
loop at a threonine residue in the T-loop resulting in full activation of
the cyclin-Cdk

Question 31

Each cyclin partner is important for

determining which specific targets are

Answer 31

subsequently phosphorylated by the Cdk

subunit

Question 32

Each cyclin-Cdk can induce different effects at

different times in the cell-cycle based upon the (3)

Answer 32

relative presence, absence or abundance of
each specific target, which can change
depending upon the phase of the cell cycle

Question 33

Activation of the — — is
prerequisite for downstream events, however
the activity of each complex is finely regulated
by additional mechanisms

Answer 33

Cyclin-Cdk complex

Question 34

Just as mutations that alter cyclin or Cdk
function can lead to misregulation of the cell
cycle, so too can mutations that

Answer 34

disrupt any of
these regulatory mechanisms create the
possibility that a cancer of some type may occur

Question 35

The activity of cyclin-Cdk is further regulated by

Answer 35

Wee1 kinase

Cdc25

Question 36

Wee1 kinase

Answer 36

further phosphorylates Cdk and renders it inactive

Question 37

Cdc25 phosphatase

Answer 37

dephosphorylates and restores activity

Question 38

APC/C is a member of the — — family of proteins

Answer 38

ubiquitin ligase

Question 39

APC/C catalyzes the (2)

Answer 39

ubiquitylation and degradation of securin and the S- and M-cyclins

Question 40

— is involved in protecting the protein linkages that hold the sister chromatids
together

Answer 40

Securin

Question 41

Securin degradation leads to

Answer 41

activation of a protease that then separates

the sisters and unleashes anaphase

Question 42

Degradation of the S- and M-cyclins leads to inactivation of the

Answer 42

Cdks

Question 43

loss of the

Cdks means that their targets can be

Answer 43

dephosphorylated by various phosphatases

that are present in anaphase, which completes M phase

Question 44

APC/C is activated in

Answer 44

mid-mitosis and remains active in G1

Question 45

APC/C is activated in mid-mitosis and remains active in G1, which provides a period
in which Cdk is —

Answer 45

inactive

Question 46

When the G1/S-Cdks are activated in late G1, — is

turned off

Answer 46

APC/C

Question 47

This allows for — accumulation to start the next cell-cycle

Answer 47

cyclin

Question 48

APC/C activity changes during the cell cycle due to its interactions with — in
anaphase and — from late mitosis through early G1

Answer 48

Cdc20

Cdh1

Question 49

Control of the Cell-Cycle by —

Answer 49

Proteolysis

Question 50

SCF

Answer 50

Ubiquitin ligase like APC/C

Question 51

SCF contains - subunits

Answer 51

3

S, C and F

Question 52

SCF

Answer 52

Ubiquitylates Cdk inhibitor (CKI) proteins in

late G1 such as p27

Question 53

Ubiquitylation of proteins is a key step in the

initiation of many proteins “marked” for

Answer 53

degradation by the proteasome complex

Question 54

— is a CKI family member that binds to the active cyclin-Cdk complex

Answer 54

p27

Question 55

p27 binds to both the

Answer 55

cyclin and the Cdk subunits

Question 56

This distorts the active

site of the — and p27 also inserts into the ATP-binding site, further

Answer 56

Cdk

inhibiting the enzyme activity

Question 57

SCF associates with an — protein that is required for

Answer 57

F-box
binding to specific
protein targets

Question 58

2 additional proteins (2) assist in the addition of multiple
ubiquitin molecules to the CKI and this targets the protein for degradation in the
proteosome complex

Answer 58

E1 and E2

Question 59

Cyclin gene expression is regulated and
specific cyclins genes are induced (turned on)
as

Answer 59

the cell cycle transitions from one phase to

the next

Question 60

Many other key regulatory proteins are

regulated at the — level

Answer 60

transcriptional

Question 61

CAK

Answer 61

phosphorylates an activating site in Cdks

Question 62

Wee1 kinase

Answer 62

phosphorylates inhibitory sites in cdks; primarily involved in suppressing cdk1 activity before mitosis

Question 63

cdc25 phosphatase

Answer 63

removes inhibitory phosphates from cdks

Question 64

p27

Answer 64

suppresses G1/S-cdk and s-cdk activities in G1

Question 65

p21

Answer 65

suppresses G1-S-cdk and S-cdk activities following DNA damage

Question 66

p16

Answer 66

suppresses G1-cdk activity in G1

Question 67

APC/C

Answer 67

catalyzes ubiquitination of regulatory proteins involved primarily in exit from mitosis, including securing and S and M cyclins; regulated by association with activating subunits

Question 68

cdc20

Answer 68

APCC activating subunit in all cells; triggers initial activation of APCC at metaphase to anaphase transition; stimulated by M-cdk activity

Question 69

cdh1

Answer 69

APCC activating subunit that maintains APCC activity after anaphase and throughout G1; inhibited by Cdk activity

Question 70

SCF

Answer 70

catalyzes ubiquitylation of regulatory proteins involved in G1 control, including some CKIs

Question 71

Cell-Cycle Control

Answer 71

The central component of the control system is the
series of cyclin-Cdk complexes that regulate
transitions through the various phases

Question 72

The complexes are also regulated by various 
inhibitory mechanisms, which provide information 
about the (3)

Answer 72

extracellular environment, DNA or cell

damage and whether each step in the cell-cycle has been properly completed

Question 73

G0 represents a

Answer 73

resting or quiescent state

Question 74

Cells can remain in G0 for

Answer 74

days to weeks or

longer before resuming proliferation

Question 75

Cells can enter G0…

Answer 75

permanently until the cell

dies

Question 76

Cells enter G0 from a cell-cycle checkpoint in the

Answer 76

G1 phase

Question 77

G0 generally occurs due to (2)

Answer 77

lack of growth factors or nutrients

Question 78

When does G0 occur in cells?

Answer 78

when they reach maturity

wells become terminally differentiated, such as nerve cells, heart muscle cells, or bone osteocytes

Question 79

The — complex
binds exclusively to
deacteylated histone
H4

Answer 79

dREAM

Question 80

what causes cells to move into G0?

Answer 80

dREAM complex

Question 81

— associated co-activators promote transcription

Answer 81

E2F

Question 82

co-repressors of either

E2F and pRB lead to histone modifications that result in (2)

Answer 82

histone compaction and

suppression of gene expression