Cell Cycle Control and Cell Division I

Question 1

Which of the following is NOT a checkpoint control in the cell cycle?

M/G1
metaphase to anaphase
Late G1
G2/M

Answer 1

M/G1

Question 2

ratio of people that get cancer:

Answer 2

1 in 3

Question 3

What is cancer?

Answer 3

uncontrolled cell growth
-inappropriate proliferation

Question 4

what are the three checkpoints if the cell cycle?

Answer 4

start checkpoint (G1)
G2/M checkpoint
metaphase-anaphase checkpoint

Question 5

what does the G1 checkpoint check for?

Answer 5

-nutrients
-growth factors
-DNA damage

Question 6

what does the G2/M checkpoint check for?

Answer 6

-cell size
-DNA replication

Question 7

what does the metaphase-anaphase checkpoint check for?

Answer 7

chromosome spindle attachment

Question 8

What three things does the cell cycle checkpoint control system depend on ?

Answer 8

-cyclically activated cyclin-dependent protein kinases
-cyclical proteolytic events
-transcriptional regulation

Question 9

What happens if the cell fails to complete an essential cell-cycle process?

Answer 9

the cycle arrests

Question 10

What does Cdk require?

Answer 10

the binding of cyclin and subsequent phosphorylation to become an active enzyme

Question 11

When is Cdk in an inactive state?

Answer 11

when there is an absence of cyclin

Question 12

What are the three steps of Cdk?

Answer 12

1. cyclin binding
2. phosphorylation
3. activation

Question 13

what is G1 cyclin?

Answer 13

cyclin D

Question 14

what Cdk is cyclin D associated with?

Answer 14

Cdk4/6

Question 15

what is G1/S cyclin?

Answer 15

cyclin E

Question 16

what Cdk is cyclin E associated with?

Answer 16

Cdk2

Question 17

what is S cyclin?

Answer 17

cyclin A

Question 18

what Cdk is cyclin A associated with?

Answer 18

Cdk2/1

Question 19

what is M cyclin?

Answer 19

cyclin B

Question 20

what Cdk is cyclin B associated with?

Answer 20

Cdk1

Question 21

How many major cyclins are in the cells?

Answer 21

4
cyclin D, E, A, and B

Question 22

does the concentration of Cdks change?

Answer 22

no

Question 23

What does the changing of cyclins being expressed allow?

Answer 23

promote transition through the cell cycle

Question 24

What initiates the metaphase to anaphase transition?

Answer 24

anaphase-promoting complex (cyclosome) APC/C

Question 25

Where does the cyclin complex get phosphorylated?

Answer 25

the T loop at a threonine residue

Question 26

What further regulates the cyclin-Cdk activity?

Answer 26

Wee1 kinase

Question 27

What does Wee1 kinase do?

Answer 27

phosphorylate Cdk and renders it inactive *adds a second inhibitory phosphate

Question 28

what does Cdc25 phosphatase do?

Answer 28

dephosphorylates inactive cyclin-Cdk and restores activity

Question 29

What is anaphase-promoting complex (cyclosome)?

Answer 29

member of ubiquitin ligase family of proteins -catalyzes the ubiquitylation and degradation of securin and the S and M cyclines

Question 30

What is securin?

Answer 30

protein involved with protecting the protein linkages that hold the sister chromatids together

Question 31

What does securin degradation do?

Answer 31

leads to activation of a protease that then separates the sisters and unleashes anaphase

Question 32

What does degradation of S and M cyclins lead to?

Answer 32

inactivation of Cdks

Question 33

What does loss of Cdks mean?

Answer 33

their targets can be dephosphorylated by various phosphatases that are present in anaphase

Question 34

When is APC/C activated?

Answer 34

in mid-mitosis and remains active in G1

Question 35

When G1/S-Cdks are activated in late G1...

Answer 35

APC/C is turned off *allows for accumulation of cyclin needed to start the next cell-cycle

Question 36

what needs to bind to APC/C to activate it?

Answer 36

Cdc20

Question 37

What is SCF?

Answer 37

ubiquitin ligase like APC/C

Question 38

How many subunits of SCF?

Answer 38

3

Question 39

What does SCF do?

Answer 39

ubiquitylates Cdk inhibitor proteins in late G1 such as p27

Question 40

What does ubiquitylation of proteins do?

Answer 40

marks proteins for degradation

Question 41

what is p27?

Answer 41

member of the CKI family that binds to activated cyclin-Cdk complex and distorts the active site of the Cdk inhibiting the enzyme activity

Question 42

What is an F-box protein?

Answer 42

a protein that associates with SCF that is required for binding to specific protein targets

Question 43

When is the G1-Cdk active?

Answer 43

in G1

Question 44

When is G1/S-Cdk active?

Answer 44

in G1

Question 45

When is S-Cdk active?

Answer 45

transition between G1 to synthesis

Question 46

When is M-Cdk active?

Answer 46

before mitosis

Question 47

What is the G0 phase?

Answer 47

resting or quiescent state -cells can remain for days to weeks or longer -can enter this until cell dies

Question 48

When does a cell typically enter G0?

Answer 48

when there is a lack of growth factors or nutrients

Question 49

What does the dREAM complex bind to?

Answer 49

deacetylated histone H4

Question 50

What phase is the dREAM complex associated with?

Answer 50

G0