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Biochem Exam 4 > Cell Cycle Control and Cell Division I > Flashcards

Cell Cycle Control and Cell Division I Flashcards

1
Q

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

M/G1
metaphase to anaphase
Late G1
G2/M

A

M/G1

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2
Q

ratio of people that get cancer:

A

1 in 3

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3
Q

What is cancer?

A

uncontrolled cell growth
-inappropriate proliferation

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4
Q

what are the three checkpoints if the cell cycle?

A

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

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5
Q

what does the G1 checkpoint check for?

A

-nutrients
-growth factors
-DNA damage

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6
Q

what does the G2/M checkpoint check for?

A

-cell size
-DNA replication

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7
Q

what does the metaphase-anaphase checkpoint check for?

A

chromosome spindle attachment

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8
Q

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

A

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

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9
Q

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

A

the cycle arrests

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10
Q

What does Cdk require?

A

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

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11
Q

When is Cdk in an inactive state?

A

when there is an absence of cyclin

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12
Q

What are the three steps of Cdk?

A
  1. cyclin binding
  2. phosphorylation
  3. activation
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13
Q

what is G1 cyclin?

A

cyclin D

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14
Q

what Cdk is cyclin D associated with?

A

Cdk4/6

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15
Q

what is G1/S cyclin?

A

cyclin E

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16
Q

what Cdk is cyclin E associated with?

A

Cdk2

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17
Q

what is S cyclin?

A

cyclin A

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18
Q

what Cdk is cyclin A associated with?

A

Cdk2/1

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19
Q

what is M cyclin?

A

cyclin B

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20
Q

what Cdk is cyclin B associated with?

A

Cdk1

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21
Q

How many major cyclins are in the cells?

A

4
cyclin D, E, A, and B

22
Q

does the concentration of Cdks change?

A

no

23
Q

What does the changing of cyclins being expressed allow?

A

promote transition through the cell cycle

24
Q

What initiates the metaphase to anaphase transition?

A

anaphase-promoting complex (cyclosome) APC/C

25
Q

Where does the cyclin complex get phosphorylated?

A

the T loop at a threonine residue

26
Q

What further regulates the cyclin-Cdk activity?

A

Wee1 kinase

27
Q

What does Wee1 kinase do?

A

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

28
Q

what does Cdc25 phosphatase do?

A

dephosphorylates inactive cyclin-Cdk and restores activity

29
Q

What is anaphase-promoting complex (cyclosome)?

A

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

30
Q

What is securin?

A

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

31
Q

What does securin degradation do?

A

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

32
Q

What does degradation of S and M cyclins lead to?

A

inactivation of Cdks

33
Q

What does loss of Cdks mean?

A

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

34
Q

When is APC/C activated?

A

in mid-mitosis and remains active in G1

35
Q

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

A

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

36
Q

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

A

Cdc20

37
Q

What is SCF?

A

ubiquitin ligase like APC/C

38
Q

How many subunits of SCF?

A

3

39
Q

What does SCF do?

A

ubiquitylates Cdk inhibitor proteins in late G1 such as p27

40
Q

What does ubiquitylation of proteins do?

A

marks proteins for degradation

41
Q

what is p27?

A

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

42
Q

What is an F-box protein?

A

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

43
Q

When is the G1-Cdk active?

A

in G1

44
Q

When is G1/S-Cdk active?

A

in G1

45
Q

When is S-Cdk active?

A

transition between G1 to synthesis

46
Q

When is M-Cdk active?

A

before mitosis

47
Q

What is the G0 phase?

A

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

48
Q

When does a cell typically enter G0?

A

when there is a lack of growth factors or nutrients

49
Q

What does the dREAM complex bind to?

A

deacetylated histone H4

50
Q

What phase is the dREAM complex associated with?

A

G0

Biochem Exam 4 (11 decks)

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