Lecture 19: Cell cycle Flashcards

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1
Q

What two processes must be aligned for cell division to occur?

A

Chromosome division and cell division

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2
Q

What is the structure of the embryonic cell cycle?

A

S and straight to M

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3
Q

What is the structure of the somatic cell cycle?

A

Alternating S and M phases
Separated by gap phases

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4
Q

What are the two steps needed for cell division to occur?

A

Nuclear division
Cytoplasm division

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5
Q

What needs to happen for a cell to enter mitosis?

A

All DNA is replicated
All DNA is damage repaired

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6
Q

What needs to happen for a cell to enter S phase?

A

Growth stimulatory signals are present
Anti-proliferative signals are absent
Sufficient nutrients

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7
Q

What drives the cell cycle engine?

A

Cdk-Cyclin complex

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8
Q

What cyclin and cdk is involved in G1?

A

Cyclin D
Cdk 4 and 6

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9
Q

What cyclin and cdk is involved in G1/S?

A

Cyclin E
Cdk 2

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10
Q

What cyclin and cdk is involved in S?

A

Cyclin A
Cdk 2

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11
Q

What cyclin and cdk is involved in M?

A

Cyclin B
Cdk 1

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12
Q

Do cdk levels stay constant or change during the cell cycle?

A

Constant

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13
Q

Do cyclin levels stay constant or change during the cell cycle?

A

Rise and fall

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14
Q

How is cdk activated?

A
  1. Cyclin binds to Cdk
  2. Conformational change pulls T loop away from Cdk active site
  3. Substrate can bind
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15
Q

What are the four different ways of regulating cyclin-cdk complexes?

A

Phosphorylation
Ubiquitin-mediated proteolysis
Binding of CKI
Localisation

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16
Q

What is the effect of phosphorylation regulation?

A

Can be inhibitory or activating

17
Q

What is the effect of regulation by ubiquitin mediated proteolysis?

A

Breaks down cyclin
Provides directionality

18
Q

What is the effect of regulation by binding of CKI?

A

Cdk inhibitors are unregulated due to damage

19
Q

What is the effect of regulation by localisation?

A

Cyclin B is imported to nucleus before mitotic

20
Q

What is the function of checkpoints?

A

Ensure cell cycle and chromosome cycle are coupled

21
Q

What is the overall process of getting in and out of mitosis?

A
  1. Switch off DNA damage checkpoints
  2. Activate Cdk1 to get into mitosis
  3. Silence spindle assembly checkpoint
  4. Inactivate Cdk1 to get out of mitosis
22
Q

What is the process of step 1 getting into mitosis?

A
  1. Signalling pathways block Cdk1 activation
  2. Override G2/M checkpoint
23
Q

What is the process of step 2 getting into mitosis?

A
  1. Cdk1 activation
  2. Phosphorylation of target proteins including other kinases
  3. Activates mitotic pathways and inactivates interphase pathways
  4. Brings about the morphological changes associated with mitosis
24
Q

What is the process of step 3 turning off mitosis?

A
  1. APC is active in mitosis
  2. When all kinetochores attached SAC is silenced and APC is activatd
  3. Cyclin B is degraded
  4. Mitotic exit
  5. Securin degraded by APC
  6. Sister chromatid separation
25
Q

What is the full overall process of turning mitosis off and on?

A
  1. DNA damage activates Wee1 to put inhibitory phosphates on Cdk1
  2. Cdc25 removes inhibitory phosphates leading to Cdk1 activation
  3. When all kinetochores are attached to spindle the APC is activated
  4. Cyclin B is ubiquitinated and degraded and Cdk1 is inactivated