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Guest Lecturers > Cell Cycle Lecture - Pfeffer > Flashcards

Cell Cycle Lecture - Pfeffer Flashcards

1
Q

The cell cycle is controlled by a complex network of what?

A

Regulatory proteins

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2
Q

The eukaryotic cell is divided into how many phases?

A

4 active ones

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3
Q

What halts the cell cycle in unfavorable conditions?

A

Checkpoints, highly conserved

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4
Q

Control is a series of what 2 counterbalances?

A

Synthesis and Degradation

Phosphorylations and dephosphorylation

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5
Q

What occurs during the M phase?

A

Mitosis and Cytokinesis

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6
Q

What does G1/G2 (gaps) allow the cell to do?

A

Monitor signals and prepare for the next phase

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7
Q

What is the basis of control for the cell cycle?

A

Cyclically activated protein kinases

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8
Q

What are some substances that disrupt microtubule function arresting the cell in M phase?

A

Colchicine, vinblastine, vincristine, taxol

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9
Q

Agents such as cytochalasin arrest in late M phase, why?

A

They disrupt microfilament structure and cytokinesis cannot occur

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10
Q

What phase to agents that inhibit DNA synthesis arrest the cell cycle in?

A

S phase

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11
Q

What cell phase occurs over the most variable amount of time?

A

G1 (6-12 hours)

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12
Q

What type of cells are not known to replicate DNA? Give a few examples.

A

Permanent cells; neurons, fat cells

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13
Q

What kind of cells have the potential to divide but await a signal? Give a few examples

A

Stable cells like hepatocytes and fibroblasts

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14
Q

What kind of cells continue to divide throughout life? Give some examples.

A

Labile cells; bone marrow cells, epithelia

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15
Q

What does the G2/M “Checkpoint” check for?

A

Is all DNA replicated, is cell big enough.

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16
Q

What does the G1/S “checkpoint” check for?

A

Is cell big enough, is environment favorable, is DNA damaged.

17
Q

What were the conclusions of Ras and Johnson nuclear fusion experiments? (4)

A

1) S phase nucleus releases something that drives G1 nucleus into S
2) G2 nucleus is resistant to S phase promoting factor
3) G1 and G2 do not influence each other
4) Mitotic nuclei release mitosis-promoting factor that affects all interphase nuclei

18
Q

G1 phase controls what aspect of proliferation in most mammalian cells? What happens if G1 does not progress to S?

A

Rate is controlled; If not ready it goes into a Sleep (G0) cycle with an RNA and protein synthesis step-down or even apoptosis when under stress

19
Q

Initiation of DNA synthesis in S phase occurs first with what? and then with? What also happens during S phase?

A

Euchromatin then Heterochromatin; Synthesis of key proteins: histones, enzymes, etc.

20
Q

What happens during G2?

A

Synthesis of proteins required for mitosis

21
Q

What phase is the best characterized that also has almost no RNA synthesis?

A

M phase

22
Q

What is the Hayflick number and how is it related to age and capacity?

A

Proliferation number; inversely related to age and capacity

23
Q

True or False. Cells have a limited lifespan.

A

True

24
Q

What is progeria?

A

Premature aging

25
Q

What are telomeres?

A

Repeated sequences of DNA at the end of chromosomes that shorted as you age; cells immortalized by overexpressing telomerase

26
Q

When do tumor cells replicate?

A

When they shouldn’t

27
Q

Why are frog eggs used in biochemical systems?

A

Large size, easy to inject, rapid division (no G1 or G2), pure cytoplasmic elements, isolated maturation promoting factor (MPF)

28
Q

What is MPF?

A

Maturation Promoting Factor, promotes maturation of Xenopus laevis oocytes

29
Q

True or false. MPF promotes mitosis in somatic cells?

A

True

30
Q

MPF activity oscillates in association with?

A

Cyclin concentration (MPF concentration is roughly constant with cyclin concentration oscillating)

31
Q

MPF is a combination of what two things?

A

Cyclin B and Cdc2 Kinase

32
Q

What is the “genetic key” to the cell cycle?

A

yeast

33
Q

How do you regulate MPF kinase activity?

A

Phosphorylation of the catalytic subunit

34
Q

How is Cdk activity regulated?

A

inhibitory proteins (p27)

35
Q

The cell cycle control system depends on cyclical proteolysis by what 2 things?

A

SCF and APC

36
Q

Regulation of APC activity controls degradation of what?

A

Cyclin B

37
Q

High cyclin B and MPF activity must be degraded to exit cell cycle, how is this done?

A

Phosphorylation

38
Q

Cyclins are controlled by what two things?

A

Gene transcription, inhibitors, phosphorylation

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