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CELL MOL > Module 2 Control of the Cell Cycle > Flashcards

Module 2 Control of the Cell Cycle Flashcards

1
Q

Typical cell cycle in Human cell (time)

A

G1 - 5 hrs (5-9)
G0 - varied
S - 7 hrs (7-10)
G2 - 3 hrs (3-4 1/2)
M - 1 hr (1/2 - 1)

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2
Q

In humans, the frequency of cell turnover ranges from ________ in early embryonic development, to an average of __________ for epithelial cells, and to an entire human lifetime spent in G0 by specialized cells, such as cortical neurons or cardiac muscle cells.

A

a few hours,
two to five days

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3
Q

When fast‐dividing mammalian cells are grown in culture (outside the body under optimal growing conditions), the length of the cycle is about

A

24 hours

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4
Q

In early embryos of fruit flies, the cell cycle is completed in about _____.

A

eight minutes

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5
Q

The timing of events in the cell cycle is controlled by mechanisms that are both ______ and ______ to the cell.

A

internal and external

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6
Q

Both the ______ and _____of cell division are triggered by _______ external to the cell when it is about to begin the replication process.

A

initiation and inhibition
events

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7
Q

An event may be as simple as (4)

A
  • death of a nearby cell
  • release of growth-promoting hormones
  • crowding of cells (inhibit)
  • size of cell
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8
Q

example of growth-promoting hormones

A

human growth hormone (HGH)

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9
Q

A lack of HGH can inhibit cell division, resulting in ______, whereas too much HGH can result in _______.

A

dwarfism
gigantism

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10
Q

as a cell grows, it becomes inefficient due to its ______________. The solution to this problem is to divide.

A

decreasing surface‐to‐volume ratio

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11
Q

three main cell cycle checkpoints and their location

A
  • G1 checkpoint - End of G1
  • G2 checkpoint - G2/M transition
  • M checkpoint - Mitotic phase (end of metaphase)
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12
Q

The integrity of the DNA is assessed at the _________. Proper chromosome duplication is assessed at the __________. Attachment of each kinetochore to a spindle fiber is assessed at the ___________.

A

G1 checkpoint
G2 checkpoint
M checkpoint

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13
Q

_________ also called _______(in yeast) determines whether all conditions are favorable for cell division to proceed

A

G1 checkpoint or restriction point (in yeast)

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14
Q

point at which the cell irreversibly commits to the cell division process

A

G1 checkpoint

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15
Q

External influences, such as _________, play a large role in carrying the cell past the G1 checkpoint

A

growth factors

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16
Q

In addition to _______ and ______, there is a check for ___________ at the G1 checkpoint

A

adequate reserves
cell size
genomic DNA damage

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17
Q

If the G1/S checkpoint detects damage, the _______ targets the cell for regulated death (________)

A

p53 protein
apoptosis

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18
Q

In G1 checkpoint, a cell that does not meet all the requirements will not be allowed to progress into the ______. The cell can halt the cycle and attempt to remedy the problematic condition, or the cell can advance into ______ and await further signals when conditions improve

A

S phase
G0

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19
Q

Cells in _________ are not actively preparing to divide. The cell is in a quiescent (inactive) stage that occurs when cells exit the cell cycle.

A

G0 phase

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20
Q

bars entry into the mitotic phase if certain conditions are not met.

A

G2 checkpoint

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21
Q

ensures that that all of the chromosomes have been replicated and that the replicated DNA is not damaged. If the checkpoint mechanisms detect problems with the DNA, the cell cycle is _______, and the cell attempts to either complete DNA replication or repair the damaged DNA

A

G2 checkpoint
halted

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22
Q
  • occurs near the end of the metaphase stage of karyokinesis
  • it determines whether all the sister chromatids are correctly attached to the spindle microtubules
A

M checkpoint

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23
Q

The M checkpoint is also known as the

A

spindle attachment checkpoint

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24
Q

During M checkpoint, the separation of the sister chromatids during anaphase is an __________, the cycle will not proceed until the kinetochores of each pair of sister chromatids are firmly anchored to at least two spindle fibers arising from opposite poles of the cell.

A

irreversible step

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25
Q

Regulator Molecules of the Cell Cycle

are direct regulators of cell cycle transitions

A
  • Cdks, cyclins, and the APC/C (positive regulators)
  • Rb, p53, and p21 (negative regulators)
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26
Q
  • either promote progress of the cell to the next phase (positive regulation) or halt the cycle (negative regulation).
  • may act individually, or they can influence the activity or production of other regulatory proteins
A

regulatory molecules

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27
Q

true or false

failure of a single regulator may have almost no effect on the cell cycle, especially if more than one mechanism controls the same event

A

true

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28
Q

True or False

the effect of a deficient or non‐functioning regulator can be wide‐ranging and possibly fatal to the cell if multiple processes are affected

A

true

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29
Q

Two groups of proteins, called ________and _______, are responsible for the progress of the cell through the various checkpoints. Cyclins regulate the cell cycle only when they are tightly bound to Cdks.

A

cyclins
cyclin‐dependent kinases (Cdks)

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30
Q

protein complex which initiates the mitotic phase of the cell cycle

A

Mitosis‐promoting factor

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31
Q

Mitosis‐promoting factor is made of two proteins:

A

Cyclin B and CDC2

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32
Q

one that oscillates in quantity during the cell cycle

A

Cyclin B

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33
Q
  • constant quantity
  • a kinase
  • encoded by the _____ gene
A

CDC2 by cdc2 gene

34
Q

True or False

CDC2 kinase is still functional when it is not combined with cyclin which is referred as cyclin‐dependent kinase (CDK)

A

False

CDC2 kinase is only functional when it is combined with cyclin which is referred as cyclin‐dependent kinase (CDK)

35
Q

permits the separation of the sister chromatids at the start of anaphase

A

anaphase‐promoting complex (APC) or cyclosome

36
Q

degrades the Cyclin B protein of MPF

A

anaphase‐promoting complex (APC) or cyclosome

37
Q

what phase does MPF activity starts

A

G2

38
Q

what phase does MPF activity starts and ends

A

G2 - M phase

check graph!

39
Q

Remember that in positive regulation, __________ cause the cycle to progress

A

active molecules

40
Q

halt the cell cycle

A

Negative regulators

41
Q

best understood negative regulatory molecules

A

Rb (Retinoblastoma proteins)
p53
p21

42
Q

a group of tumor-suppressor proteins common in many cells

A

retinoblastoma protein

43
Q

The 53 and 21 designations refer to the ___________ of the proteins (p) in ________

A

functional molecular masses
kilodaltons

44
Q

All three of these regulatory proteins were discovered to be ______ or ___________ in cells that had begun to replicate uncontrollably (became ___________). In each case, the main cause of the unchecked progress
through the cell cycle was a faulty copy of the regulatory protein.

A

damaged or non‐functional
cancerous

45
Q

Cancer cells can become tumors

___ remain clustered and can be removed

____ are able to ___ or break away and form new tumors

____ are substances that promote cancer

A

Benign tumors

Malignant tumors
Metastasize

Carcinogens

46
Q

Rb, p53, and p21 act primarily at the _____ checkpoint

A

G1 checkpoint

47
Q

is a multi‐functional protein that has a major impact on the commitment of a cell to division because it acts when there is damaged DNA in cells that are undergoing the preparatory processes during G1.

If damaged DNA is detected, it halts the cell cycle and recruits enzymes to repair the DNA

A

p53

48
Q

If the DNA cannot be repaired, ______ can trigger ______, or cell suicide, to prevent the duplication of damaged chromosomes

A

p53
apoptosis

49
Q

As p53 levels rise, the production of ____ is triggered

A

p21

50
Q

enforces the halt in the cycle dictated by p53 by binding to and inhibiting the activity of the Cdk/cyclin complexes

A

p21

51
Q

As a cell is exposed to more stress, higher levels of p53 and p21 accumulate, making it less likely that the cell will move into the

A

S phase

52
Q
  • exerts its regulatory influence on other positive regulator proteins.
  • monitors cell size
A

Rb

53
Q

In the active, dephosphorylated state, Rb binds to proteins called _____________, most commonly, _____.

A

transcriptions factors,
E2F

54
Q

“turn on” specific genes to produce certain proteins

A

transcriptions factors

55
Q

When Rb is bound to ______, production of proteins necessary for the G1/S transition is blocked. As the cell increases in size, Rb is slowly ________until it becomes inactivated.

A

E2F
phosphorylated

56
Q

As Rb releases E2F, it _____ the gene that produces the transition protein, and this particular block is removed.

A

“turned on”

57
Q

For the cell to move, past each of the checkpoints, all positive regulators must be ______ and all negative regulators must be ______

A

turned on
turned off

58
Q

Rb and other proteins that negative regulate the cell cycle are sometimes called ______

A

tumor suppressors

59
Q

Apoptosis is also known as ____

It occurs in normal development when cells are temporarily required for a maturation process. It also occurs in genetically damaged cells and older cells that rare no longer necessary.

An example being (2)

A

Programmed Cell Death

Embryonic Development
Metamorphosis

60
Q

A well-known example of apoptosis is in the animal ____

It is signaled by the ____ which causes the animal to digest their tail cells, reabsorbing and recycling the digestion products into new structures

A

Frog (frog metamorphosis)
Thyroid hormone

61
Q

Cells that die from an unexpected injury undergo ____ which is an accidental death.

A

Necrosis

62
Q

In nectrotic cells,

  • the ____ does not shrink or fragment
  • nuclear morphology changes
  • ____ form but fuse (enlarge)
  • no _______ in blebs
  • the ____ bursts to release the cell contents into the extracellular environment
  • organelles are ______
A

nucleus
Blebs
organelles
cell membrane
non-functional

63
Q

In apoptosis,

  • Nucleus ____
  • the blebs turn into ____
  • ______ spread to blebs
  • _______ are not released into the extracellular environment
  • organelles still _____
A

fragment
apoptotic bodies
organelles
cell contents
functional

64
Q

Cell Division Rate

  1. skin cell
  2. RBC
  3. liver cell
  4. intestine (internal lining)
  5. intestine (muscle and other tissues)
A
  1. skin cell - 2 weeks
  2. RBC - 4 months
  3. liver cell - 300-500 days
  4. intestine (internal lining) - 4-5 days
  5. intestine (muscle and other tissues) - 16 years
65
Q

P21 inhibits CDK __, ___, ___, & ___

A

CDK 2, 3 ,4, & 6

66
Q

Environment determines what form of reproduction is most advantageous.
* _______ is an advantage in consistently favorable conditions.
* _______ is an advantage in changing conditions.

A

Asexual reproduction
Sexual reproduction

67
Q

Asexual reproduction (3)

A
  • Budding
  • Fragmentation
  • Vegetative reproduction
68
Q

forms a new organism from a small projection growing on the surface of the parent.

A

budding

69
Q

is the splitting of the parent into pieces that each grow into a new organism.

A

fragmentation

70
Q

forms a new plant from the modification of a stem or underground structure on the parent plant

A

Vegetative reproduction

71
Q

________ cells perform specific functions. Cells develop into their mature forms through the process of ____________. Cells differ because different combinations of _______ are expressed. A cell’s _____ in an embryo helps determine how it will differentiate

A

Specialized cells
cell differentiation
genes
location

72
Q
  • are unique body cells
  • have the ability to:
  • divide and renew themselves
  • remain undifferentiated in form
  • develop into a variety of specialized cell types
A

stem cells

73
Q

Stem cells are classified into three types

A

totipotent
pluripotent
multipotent

74
Q

growing into any other cell type

A

totipotent

75
Q

growing into any cell type but a totipotent cell (almost any cell)

A

pluripotent

76
Q

growing into cells of a closely related cell family

A

multipotent

77
Q

Stem cells come from _____ and ________

A

adults and embryos

78
Q
  • can be hard to isolate and grow
  • use of these may prevent transplant rejection.
A

Adult stem cells

79
Q
  • are pluripotent and can be grown indefinitely in culture
  • use of this raises ethical issues
A

embryonic stem cells

80
Q

The use of ______ offers many currently realized and potential benefits.

  • are used to treat leukemia and lymphoma.
  • may cure disease or replace damaged
    organs.
  • may revolutionize the drug development
    process.
A

stem cells

CELL MOL (9 decks)

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