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COB Molecular > 3.1 Cell Cycle > Flashcards

3.1 Cell Cycle Flashcards

1
Q

What is the 4 phases of the cell cycle?

A

G1, S, G2, M

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2
Q

What happens in S phase?

A

DNA synthesis

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3
Q

What happens in M phase?

A

Separate chromosomes and divide cells

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4
Q

What are GAP phases used for?

A

Allows more time for growth

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5
Q

What are the 3 checkpoints in the cell cycle?

A

Checkpoint I Start, Checkpoint II G2/M, Checkpoint III metaphase to anaphase

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6
Q

What are the 3 checkpoints in the cell cycle?

A

Checkpoint I Start, Checkpoint II G2/M, Checkpoint III metaphase to anaphase

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7
Q

What does Checkpoint I Start do?

A

Cell commits to cell cycle entry and chromosome duplication

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8
Q

What does checkpoint II G2/M do?

A

Chromosome alignment on spindle in metaphase

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9
Q

What does checkpoint III do?

A

Trigger sister chromatid separation and cytokinesis

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10
Q

The cell cycle control system uses a series of biochemical switches made of what?

A

Cdks

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11
Q

What do Cdks turn on and do?

A

Turn on various steps of the cell cycle and P proteins downstream to activate them and regulate cell cycle events

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12
Q

What is the heart of the cell-cycle control system?

A

Cdks

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13
Q

True or False? Cdks levels remain constant during cell cycle

A

False. Rise and fall

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14
Q

The cell cycle is governed by what?

A

Cdks

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15
Q

True or False? Cdks activities remain constant during cell cycle

A

False. Rise and fall

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16
Q

What proteins regulate cdks?

A

cyclins

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17
Q

Cdks are dependent on what?

A

cyclins

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18
Q

Cdks must be bound to cyclin to have what type of activity?

A

protein kinase

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19
Q

True or False? Without cyclin, cdk inactive

A

True

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20
Q

cyclin expression in cells controls what?

A

what step cell is in the cell cycle

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21
Q

What directs cdks to their specific target?

A

cyclins

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22
Q

What directs cdks to their specific target?

A

cyclins

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23
Q

what are the 4 classes of cyclins?

A

G1/S, S, M and G1

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24
Q

What 4 things do the G1/S cyclins do?

A

Activate Cdks in late G1. Help trigger progression through START. Commitment made to cell cycle entry. Levels drop in S phase

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25
Q

What 4 things do S cyclins do?

A

duplicate DNA, bind Cdks after progression through START, help stimulate chromosome duplication, S-cyclin levels remain high until mitosis

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26
Q

What do the M-Cyclins do?

A

Activate cdks that stimulate entry into mitosis at G2/M checkpoint. M-cyclins removed at mid-mitosis

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27
Q

What do G1 cyclins do?

A

Govern activity of G1/S cyclins

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28
Q

What of cdks rise and fall during the cell cycle?

A

Activities

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29
Q

What of cyclins rise and fall during the cell cycle?

A

Levels

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30
Q

What of cyclins rise and fall during the cell cycle?

A

Levels

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31
Q

Without cyclin bound, the active site of cdk is blocke by a region of the protein called what?

A

T loop

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32
Q

What causes the T-loop to move out of the active site?

A

Binding of cyclin to cdk

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33
Q

P of Cdk at t-loop does what to the enzyme?

A

Fully activates it

34
Q

What P cdk?

A

CAK

35
Q

What two proteins inhibit Cdk activity?

A

Wee1 kinase and CKI

36
Q

How does Wee1 kinase inhibit Cdk activity?

A

By P the roof site

37
Q

What enzyme reverses Wee1 kinases P of the roof site?

A

Cdc25

38
Q

How does CKI inhibit cdk activity?

A

CKI binds to both cdk and cyclin to inactivate it

39
Q

What is the primary purpose for CKI to inhibit cdk activity?

A

To control G1/S cdks + S cdks early in cell cycle.

40
Q

What is p53?

A

tumor suppressor

41
Q

What does p53 influence?

A

expression of many genes

42
Q

p53 up regulates what?

A

p21

43
Q

what is p21?

A

a CKI to stop cell division

44
Q

What is a target of p53?

A

p21 transcription

45
Q

how does cancer happen pertaining to p53 and p21?

A

If p53 fails there will be lower p21 expression and without this CKI cells divide uncontrollably.

46
Q

What is another control of cyclin-cdk activity at S phase?

A

Proteolysis

47
Q

S cyclin cdk complex is important to start what?

A

DNA replication

48
Q

How are s-cyclin cdk complexes inhibited by?

A

Binding to CKI

49
Q

How does s cyclin cdk complexes release CKI?

A

proteolysis

50
Q

How does CKI get removed from s-cyclin cdk?

A

By an enzyme called SCF-ubiquitin ligase that adds ubiquitin to CKIs

51
Q

SCF activity depends on what?

A

F-Box subunit

52
Q

What part of the cell cycle does SCF add ubiquitin to CKI?

A

G1

53
Q

What controls mitosis?

A

M cyclin-cdk

54
Q

Why is M-cdk usually in the inactive form?

A

Wee1 holds M-cdk in inactive state

55
Q

What phase of the cell cycle has lots of primed inactive M-cdk around?

A

G2

56
Q

What activated M-cdk?

A

Cdc25

57
Q

What type of feedback is m-cdk activation?

A

positive

58
Q

What is mitosis?

A

Progression from metaphase to anaphase

59
Q

How is mitosis triggered?

A

By protein destruction

60
Q

What is a key regulator for mitosis?

A

APC/C

61
Q

What family is APC/C part of?

A

ubiquitin ligase

62
Q

What does APC/C do?

A

addition of ubiquitin to proteins to cause destruction

63
Q

What two major proteins are affected by APC/C?

A

Cohesion and securin

64
Q

What does cohesin do?

A

glues together sister chromatids

65
Q

What does securin do?

A

protects cohesin proteins linkages

66
Q

What does separase do?

A

undoes glue holding chromatids together

67
Q

how does securin protect cohesins?

A

inhibits separase.

68
Q

What is the order of APC/C and mitosis?

A

APC/C levels rise in mid mitosis, APC/C adds ubiquitin on targets, APC/C destroys cyclins and complexes, destruction of securin, separase active thus cleaves cohesin, sister chromatids come apart.

69
Q

What enzymes are a major target for APC/C?

A

S and M cyclins

70
Q

How is APC/C activated?

A

by binding to Cdc20

71
Q

When moving to anaphase APC/C wants to get ride of what two enzymes?

A

S and M cyclin

72
Q

What are the first 4 steps of the cell cycle control system?

A
  1. Activation of G1-cdk. 2. G1 cdk stimulated genes making G1/S-cyclin + S-cyclin. 3. Go through START checkpoint. 4. G1 S cdk activity induces S cdk activity causing DNA replication
73
Q

What are the final 3 steps of the cell cycle control system?

A
  1. M cdk drives expression through G2/M checkpoint. 6. APC/C + Cdc20 triggers destruction of securin and cyclins at metaphase to anaphase transition. 7.Completion of mitosis.
74
Q

Mitosis cell cycle regulation occurs in 2 parts, what are they?

A
  1. Increase of M cdk activity at G2/M triggers prophase, prometaphase and metaphase. 2. Metaphase-to anaphase transition
75
Q

What happens during the first part of the cell cycle regulation

A

assembly of mitotic spindle, and attachement to sister chromatids

76
Q

what happens during the 2nd part of the cell cycle regulation?

A

APC/C destroys securin, which securin can no longer inhibit separase thus cleaves cohesin. APC/C triggers destruction of cyclins that leads to cdk inactivation and de P of cdk targets

77
Q

For DNA replication what 2 problems must the cell solve?

A

Replication of DNA with complete accuracy and every nucleotide is copiesd once to prevent amplification

78
Q

Describe the 3 checkpoints in the cell cycle*

A

Checkpoint I Start: Cell commits to cell cycle entry and chromosome duplication, Checkpoint II G2/M: Chromosome alignment on spindle in metaphase, Checkpoint III metaphase to anaphase: Trigger sister chromatid separation and cytokinesis

79
Q

Name 2 ways of regulating cyclin cdk complexes*

A

inhibitory proteins:Wee1 kinase and CKI and APC/C

80
Q

Describe the order of events involving APC/C cdc20, securin, separase and cohesin in sister chromatid separation.

A

APC/C levels rise in mid mitosis by activation of Cdc20, APC/C adds ubiquitin on targets, APC/C destroys cyclins and complexes, destruction of securin, separase active thus cleaves cohesin, sister chromatids come apart.

COB Molecular (36 decks)

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