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Enzymes > Cell cycle > Flashcards

Cell cycle Flashcards

1
Q

What is the G1 phase?

A

A growth period preceeding DNA synthesis

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2
Q

What is the is the S phase

A

DNA synthesis phase

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3
Q

What is the G2 phase?

A

Second period of growth where there is x2 DNA

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4
Q

Where are the checkpoints located?

A

G1/S and G2/M

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5
Q

What is the G1/S checkpoint called? What is the cell doing?

A

The restriction point

Checking to see if division is favorable

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6
Q

At the G2/M checkpoint, what is the cell doing?

A

Checking to make sure that all of the DNA has been replicated

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7
Q

What is the cell doing at the metaphase/anaphase transition point?

A

Evaluating all of the chromosomes to ensure that they are attached to the mitotic spindle

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8
Q

What is the DNA damage checkpoint? When does it occur?

A

Check to ensure there is no damaged DNA in the cell.

All the time.

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9
Q

Progress through the cell cycle is driven by what family of enzymes? What proteins?

A

Cyclin dependent kinases, which are regulated by cyclins

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10
Q

What cyclins/ CDKs are present in the M phase?

A

Cycline A, B and CDK1

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11
Q

What cyclins/ CDKs are present in the Mid G1 phase?

A

Cycline D and CDK4, CDK6

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12
Q

What cyclins/ CDKs are present in the late G1 phase?

A

Cyclin E and CDK2

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13
Q

What cyclins/ CDKs are present in the S phase?

A

Cyclin A and CDK 2

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14
Q

How are cyclins degraded?

A

By ubiquitin dependent proteolysis

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15
Q

What does the anaphase promoting complex do in the last part of M phase?

A

Ubiquinates cyclin B, marking it for destruction and triggering G1 phase

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16
Q

How are CDKs regulated (generally)?

A

de/phosphorylation and CDK inhibitors

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17
Q

What are mitogenic signals?

A

Tissue specific growth factors

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18
Q

Most differentiated cells are in what stage?

A

G0

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19
Q

Do cell-cell interactions promote or inhibit cell division?

A

Inhibit

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20
Q

Do cell-ECM interactions promote or inhibit cell division?

A

Promote

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21
Q

What is the action of c-Fos?

A

Stimulate the transcription of delayed response genes

22
Q

What are early response genes?

A

Genes that are stimulated very soon after the addition of growth factors

23
Q

What do delayed response factors encode?

A

Mid-G1 cyclins and CDKs

Late G1 cyclins and CDKs

24
Q

What type of kinase is the growth factor receptor?

A

Tyrosine kinase

25
Q

What is the order of the assembled complex that binds to the growth factor receptor?

A

GRB2, Sos, and Ras

26
Q

What type of cascade is the growth factor cascade?

A

MAP-kinase cascade

27
Q

What does Sos do?

A

Promotes the phosphorylation of Ras to the GTP bound form

28
Q

What does Ras activate? What class is this molecue?

A

Raf–a protein kinase

29
Q

What is the action of Raf?

A

phosphorylates MAP kinase kinase

30
Q

What is the action of MAP kinase kinase? What does that molecule do?

A

Phosphorylates MAP kinase, which enter the nucleus and activates c-Fos transcription

31
Q

True or false: growth factors are still needed after c-Fos is activated?

A

False

32
Q

What is the target for CDK4/6 complex?

A

Rb protein–they phosphorylate this

33
Q

What are Rb proteins?

A

Proteins that bind to, and inhibit E2F proteins

34
Q

What are E2F proteins?

A

Transcription factor that activates the late G1 cyclin, S phase cyclin, and the S-phase CDK

35
Q

What is the function of the E2F/Rb complex?

A

Recruit HDACs–inhibit DNA transcription

36
Q

What does phosphorylation of the Rb/E2F complex by CDK4/6 complex do?

A

Separates Rb ad E2F, allowing E2F to function

37
Q

Cyclin E and CDK2 are generated by E2F. What does this complex do?

A

Autostimulates E2F disassociation from Rb

38
Q

What is the action of INK4 proteins?

A

Specificially inhibit CDK4/6 activity by competing with cyclin D for binding with CDK4/6.

39
Q

What is the action of p27KIP1?

A

Inhibits cyclin A-CDK2 (the cyclin/CDK in S phase) by binding the cyclin A/CDK2 complex

40
Q

Phosphorylation of p27KIP1 does what?

A

Disassociates p27KIP1 from the cyclin A/CDK2 complex, allowing the complex to phosphorylate (activate) the origins of replication for DNA synthesis

41
Q

What does the CyclinA/CDK2 complex do?

A

Phosphorylates the origins of replication and begins the synthesis of DNA

42
Q

When is cyclin A present? Cyclin B?

A

A from the beginning of S

B from late in S

43
Q

CDK1/cyclin A (or B) are inactivated until what time? How are the activated? What do they do?

A

Activated after DNA has been fully replicated
Phosphorylation actives them
Activate mitosis

44
Q

What is the function of ATM?

A

It detects replication forks, activating another kinase to prevent dephosphorylation of cyclin/CDK1

45
Q

What complex is inhibited when kinetochores are not associated with a spindle fiber?

A

Anaphase promoting complex

46
Q

What is the action of p27KIP1 ?

A

inhibition of the cyclinA/CDK2 complex (which activates S phase)

47
Q

What is the action of p53 protein?

A

Activates p21CIP1.

48
Q

What is the action of p21CIP1?

A

Inhibits BOTH cyclin/CDK1 and cyclin CDK2 commplexes, completely stopping progression of the cell.

49
Q

Assume there is a double stranded break in DNA. What protein will detect this? Describe the signalling pathway leading to inhibition of further cell progress (Hard, 3 steps in the pathway).

A
  1. ATM/ATR detect DNA break, activate p53
  2. p53 activated p21^KIP1
  3. Inhibition of CDK2/cyclin E, and CDK1/cyclinA
50
Q

Defects in genes that encode ATM/ATR leads to what disease?

A

Ataxia telangiectasia

Enzymes (24 decks)

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