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Cancer Biology > The Cell Cycle and Cancer > Flashcards

The Cell Cycle and Cancer Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What happens in G1 checkpoint?

A

Makes sure there is enough energy and senses external cues, e.g. needing space

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2
Q

What happens in G2 checkpoint?

A

Mainly detects DNA damage and sees if the cell can repair them

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3
Q

What happens in M checkpoint?

A

Allows chromosomal segregation to occur correctly

Determines if the chromosomes are attached correctly to the microtubule

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4
Q

When are CDKs active?

A

When cyclins are bound

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5
Q

What do CDKs do?

A

Phosphorylate a number of proteins which drive the cell cycle

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6
Q

Why are CDKs inactive normally?

A

Their active sites are blocked so their is no substrate or ATP binding

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7
Q

What is the role of cyclins?

A

To activate CDKs

They provide substrate specificity

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8
Q

What do mitogens do?

A

Activate TFs, e.g. Myc and Fos, to induce cyclin D

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9
Q

What does E2F do?

A

Induce cyclin E and A

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10
Q

What does FoxM1 do?

A

Induces cyclin B

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11
Q

What does cyclin D activate?

A

E2F

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12
Q

What does cyclin A activate?

A

FoxM1

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13
Q

What ubiquitin ligases degrade cyclin E?

A

SCF ligase (Skp, Cullin and F-box)

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14
Q

What ubiquitin ligase degrades cyclin A and B?

A

Anaphase promoting complex/ Cyclosome (APC/C)

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15
Q

What is the advantage of sing protein degradation in the cell cycle?

A

Unidirectional movement

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16
Q

Describe the positive feedback mechanism of cyclinB:CDK1

A

CyclinB:CDK1 is inhibited by Wee1/My1 which causes CDK1 phosphorylation
When cyclinB:CDK1 is in the active conformation, it inhibits Wee1/My1 and activates CDC25 phosphatase to dephosphorylate CyclinB:CDK1 so more is in the active conformation

17
Q

Describe the positive feedback mechanism of cyclinE:CDK2

A

Mitogens induce the binding of p27 (inhibitor) to cyclinE:CDK2
When cyclinE:CDK2 is in the positive conformation, it phosphorylates and inhibits p27

18
Q

What inhibits the phosphorylation of p27 by CyclinE:CDK2?

A

SCF ligase

19
Q

When is E2F in an inactive form?

A

When it is bound to Rb

20
Q

What inhibits the binding of Rb to E2F?

A

Phosphorylation by CyclinD:CDK4/6

21
Q

What stimulates CyclinD:CDK4/6?

A

Growth conditions

22
Q

What percentage of tumours are aneuploid?

A

80-90%

23
Q

What is chromosomal instability caused by?

A

Frequent errors in mitosis

24
Q

What is chromosomal instability associated with?

A

Poor patient prognosis
Metastasis
Resistance to chemotherapies

25
Q

What phenotype is worse, having too many or too little chromosomes?

A

Having too many

26
Q

What happens during the mitotic checkpoint?

A

Unattached kinetochores produce mitotic checkpoint complex (MCC) -> Inhibits the anaphase promoting complex (APC) -> when all kinetochores are attached then MCC production stops -> APC becomes active and degrades Cyclin B and Securin -> Mitosis

27
Q

How do microtubules bind to kinetochores?

A

Randomly

Negatively charged microtubules bind to positively charged kinetochores

28
Q

What is securin?

A

An inhibitor of separase

29
Q

What is separase function?

A

It cleaves the bond which holds sister chromatids together

30
Q

What is the process of error correction?

A

Aurora B removes kinetochore-microtubule attachments -> Correct attachments pull away from aurora B -> These are then insensitive to aurora B -> Allows specific correction of attachment errors

31
Q

In terms of the cell cycle, why are tumour suppressors important?

A

Without tumour suppressors, the cyclins are not degraded and cell cyclin will continue when it is not meant to

32
Q

What CDK binds to cyclin E?

A

CDK2

33
Q

What CDK binds to Cyclin D?

A

CDK4/6

34
Q

What CDK does Cyclin B bind to?

A

CDK1

Cancer Biology (13 decks)

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