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BMS 100 > The Cell Cycle > Flashcards

The Cell Cycle Flashcards

1
Q

The cell cycle consists of (2)

A
  • Mitotic (M) phase (mitosis and cytokinesis)
  • Interphase (cell growth and copying of chromosomes in
    preparation for cell division)
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2
Q

Interphase (about 90% of the cell cycle) can be divided into subphases:

A
  • G1 phase: first gap
  • S phase: synthesis
  • G2 phase: second gap
  • G0 phase: resting phase, postmitotic quiescent
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3
Q

the first gap phase

A

G1 phase: first gap

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4
Q

Preparatory growth phase prior to cell entering DNA synthesis phase

A

G1

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5
Q

what cells are metabolically active during G1

A
  • Requires nutrients & growth factors
  • RNA, protein, lipid and carbohydrate synthesis occurs
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6
Q

Duration of G1. It is ____ in embryonic and cancer cells and __________ in rapidly dividing cells

A

Duration: variable (6-24hrs)
short and Rapid or non-existent

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7
Q

where DNA and chromosomal protein
synthesis occurs

A

Phase s

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8
Q

Duration of S phase

A

lasts approximately 7-8 hours in a typical mammalian cell with
a 16 hour cycle

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9
Q

In S phase, __________ are no longer needed. __________ occurs here, creating
two identical ______________

A

Growth factors no longer needed

DNA replication occurs here, creating two identical daughter genomes

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10
Q

what is second growth phase

A

G2

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11
Q

Interval between DNA synthesis (S phase)
and mitosis (M phase)

A

G2

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12
Q

synthesize of what occurs during G2 phase. Does cell growth continue?

A

enzyme, protein and ATP synthesis occur

yes, cell growth continues

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13
Q

Duration of G2

A

lasts approximately 3 hours in a typical mammalian cell with a 16-hour cycle

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14
Q

what is the mitotic phase where the cell undergoes mitosis and then cytokinesis?
What is the duration of this phase?

A

Mitotic phase
Duration: 1-2 hours

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15
Q

State of withdrawal from cell cycle. Cell is neither dividing nor preparing to divide

A

G0 phase

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16
Q

in what phase, is the cell described to be “doing its job” - performing its function within the tissue

A

G0 phase

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17
Q

Examples of cells in G0:

A

Hepatocytes, neurons

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18
Q

Checkpoints are based on a series of biochemical switches to initiate specific cell-cycle events.

A

cell cycle control system

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19
Q

Checkpoints are based on a series of ______________ to initiate specific cell-cycle events.

A

biochemical switches

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20
Q

Feature of the biochemical switches: Generally ______ (on/off) to launch an event in a complete & irreversible fashion

A

binary

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21
Q

what are the 3 features of biochemical switches?

A
  1. they are binary
  2. they are robust and reliable
  3. they are adaptable and modified to suit specific cell types
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22
Q

where are modifications to the cell cycle control system usually seen?

A

Cyclin dependent kinases (Cdks)

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23
Q

Points in the eukaryotic cell division cycle where progress through the cycle can be halted until conditions are suitable for the cell to proceed to the next stage

A

Checkpoints aka “Transitions”

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24
Q

Checkpoints can be regulated by:

A
  • Factors within the cell, mostly controlled by the “health” or “state of preparation” of the cell
  • Factors from outside the cell – i.e. messages from other cells within the same tissue or distant cells
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25
Q

Three major regulatory transitions at the:

A
  1. Start Transition (aka G1/S)
  2. G2/M transition
  3. Metaphase-to-anaphase transition (aka M-to-A)
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26
Q

For most cells, the ____ seems to be the rate-limiting and committing step of the cell cycle

A

G1/S
at every stage after this, the cell will either have to divide or it will die

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27
Q

what checkpoint would you ask: is the environment favourable?

A

G1/S

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28
Q

what checkpoint would you ask: is all the DNA replication? Is the environment favourable?

A

G2/M transition

29
Q

what checkpoint would you ask: are all the chromosomes attached to the spindle?

A

Metaphase-to-anaphase transition (aka M-to-A)

30
Q

Cdks are controlled a group of proteins called

A

cyclins

31
Q

There are 4 classes of cyclins that form specific complexes with Cdks

A
  1. G1 cyclins: Cyclin D
  2. G1/S cyclins: Cyclin E
  3. S-cyclins: Cyclin A
  4. M cyclins: Cyclin B
32
Q

Forms complex with Cdk4 or Cdk 6

Involved in G1 phase of cell cycle, needed for initiation of transcription of G1/S cyclins to help promote passage through start transition

A

G1 cyclins: Cyclin D

33
Q

Cdks are responsible for cyclical changes in
_______________ of intracellular proteins that
initiate/ regulate the major events of the cell cycle

A

phosphorylation

34
Q

Cyclical changes in cyclin protein levels result in the
cyclic assembly and activation of ________________ at specific stages of the cell cycle.

A

cyclin–Cdk complexes

35
Q
  • Forms complex with Cdk2
  • Bind Cdk’s at the end of G1 & help trigger progression through start transition
  • Levels decrease in S phase
A

G1/S cyclins: Cyclin E

36
Q
  • Forms complex with Cdk1 and Cdk2
  • Bind Cdks after progression through start transition & helps stimulate chromosome duplication during S phase
  • Levels remain elevated until mitosis; contributes to control of some early mitotic events
A

S-cyclins: Cyclin A

37
Q
  • Forms complex with Cdk1
  • Bind CdKs to stimulate entry into mitosis at the G2/M transition
  • Levels decrease in mid-mitosis
A

M cyclins: Cyclin B

38
Q

Cyclin D and CDK 4 and 6 create which cyclin-cdk complex?

A

G1-CDK

39
Q

Cyclin E and CDK 2 create which cyclin-cdk complex?

A

G1/S-CDK

40
Q

Cyclin A and CDK 2 and 1 create which cyclin-cdk complex?

A

S-CDK

41
Q

cyclin B and CDK 1 create which cyclin-cdk complex?

A

M-CDK

42
Q

which cyclin-cdk complex is needed for progression through the start transition. What is it made up of?

A

G1-CDK - Cyclin D, CDK 4, and CDK6

43
Q

which cyclin-cdk complex is needed to trigger progression through the start transistion. What is it made up of?

A

G1/S-CDK made up of Cyclin E and Cdk 2

44
Q

which cyclin-cdk complex is to stimulate chromosome duplication and is involved in early mitotic events? What is it made up of?

A

S-CDK made up of the Cyclin A, CDK2 and CDK1

45
Q

which cyclin-cdk complex is needed to stimulate progression through the G2/M checkpoint. What is it made up of?

A

M-CDK is made up of cyclin B and cdk 1

46
Q

How do cyclin-Cdk complexes work?

A

Cyclins function by activating (phosphorylating) the Cdk

Cyclin protein does not simply activate its Cdk partner,
but also directs it to a specific target protein

47
Q

Progression through the _____________ checkpoint is a little different

A

Metaphase-to-anaphase

48
Q

the anaphase promoting complex (APC) is a member of what ligase family of enzymes

A

ubiquitin

49
Q

What is APC used for?

A

to stimulate proteolytic destruction of specific regulatory proteins

50
Q

What proteins do APC target for destruction?

A

securin, M-cyclins, S-cyclins

51
Q

how does a Metaphase-to-anaphase checkpoint occur?

A

Occurs via regulated proteolysis

52
Q

what happens when you ubiquitin something?

A

You target it for destruction

Ubiquitin is used to stimulate the proteolytic destruction of specific regulatory proteins

53
Q

Early response genes are usually

A

usually transcription factors

54
Q

Delayed response gene are usually

A

usually Cdks, cyclins, or other proteins needed for cell division

55
Q

G1/S checkpoint: Active G1-cdk (and G1/S-cdk)
complex will target a protein called ___ and phosphorylate it

A

RB

56
Q

RB functions as a transcription co-repressor. Hyperphosphorylation of RB will ___________ RB

A

inactivate RB

Inactive RB then releases a transcription factor E2F,
allowing transcription to proceed

57
Q

Progression through G1 is delayed if:

A
  • DNA is damaged by radiation, chemicals, or errors
  • Absence of nutrients or growth factors
  • Abnormal cell size
58
Q

Entry into M is prevented when:

A
  • DNA replication is not complete
  • Presence of DNA damage
  • Abnormal cell size
59
Q

Progression through M-to-A is prevented if

A

Chromosomes are not properly attached to mitotic spindle

60
Q

How is the cell cycle paused in unfavourable conditions? Two important molecular mechanisms:

A
  • Cdk inhibitory proteins (CKIs)
  • Proteins coded by tumour suppressor genes
61
Q

what molecule is primarily used by cells to govern the activities of G1/Sand S-Cdks early in cell cycle

A

CKIs
Binding of Cdk inhibitory protein (CKI) inactivates cyclin-Cdk complex

62
Q

CyclinD-cdk4 & CyclinD-cdk5 (G1-cdk complex) are inhibited by

A

p16

63
Q
  • CyclinE-cdk2 (G1/S-cdk complex)
  • CyclinA-cdk2 & CyclinA-cdk1 (S-cdk complex)
  • Cyclin B-cdk1 (M-cdk complex)
    are all inhibited by
A

p21

64
Q
  • CyclinA-cdk2 & CyclinA-cdk1 (S-cdk complex)
  • CyclinE-cdk2 (G1/S-cdk complex)
  • Cyclin B-cdk1 (M-cdk complex
    are all inhibited by
A

p27

65
Q

p53 and RB are examples of

A

Tumour suppressor genes

66
Q

what tumour suppressor gene recognizes and binds damaged DNA

A

p53
Unstressed cells have lower levels of p53 since it will be bound by a protein called Mdm2 and be degraded

67
Q

what tumour suppressor gene is generally found in active form (hyperphosphorylated) and can recognize damaged DNA

A

RB

68
Q
A

BMS 100 (37 decks)

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