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BISC 372 > 1.5 Introduction to the Cell Cycle, Genome Replication > Flashcards

1.5 Introduction to the Cell Cycle, Genome Replication Flashcards

1
Q

What is the function of the cell cycle (2)?

A
  1. duplicate the genome
  2. segregate chromosome copies into two genetically identical daughter cells
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2
Q

Genome duplication occurs in [ ] phase.

A

S

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3
Q

Chromosome segregation, and cell division occur in [ ] phase. There are two parts of the M phase: [ ].

A
  1. S Phase
  2. Mitois: nuclear division
  3. Cytokinesis: cytoplasmic division
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4
Q

S phase yields duplicate DNA to be divided among [ ].

A

The first step of mitosis, [ ], involves the [ ] of DNA within the cell

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5
Q

DNA is condensed into [ ] linked via [ ].

A
  1. sister chromatids
  2. sister chromatid cohesion
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6
Q

The nuclear envelope will begin to break down, and sister chromatids will become bound to the [ ].

A

mitotic spindle

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7
Q

What is the mitotic spindle?

A

a collection of microtubules tasked with the separation of sister chromatids

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8
Q

Through the [ ], sister chromatids are attached to opposite poles of the cell

A

spindle

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9
Q

In metaphase, sister-chromatids align at the [ ].

A

cellular equator

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10
Q

In anaphase, the cohesion comes to an end, as chromatids are pulled towards [ ].

A

opposite poles

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11
Q

In telophase, the spindle breaks down, and chromatids are packaged into [ ].

A

different nuclei

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12
Q

In cytokinesis, the cell splits into two, each inheriting a [ ].

A

nucleus

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13
Q

S phase and M phase are two parts of the cell cycle, separated by [ ]

A

gap phases, G1 and G2

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14
Q

What is the order of the cell cycle?

A

G1 phase, S phase, G2 phase, M phase

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15
Q

The overall order of the cell cycle is collectively known as [ ].

A

interphase

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16
Q

What do the gap phases allow for (2)?

A
  1. the cell to grow
  2. cell to ensure the conditions are right before committing to S phase and mitosis (G1 phase)
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17
Q

What are the central components of cell cycle control (4)?

A
  1. cyclin-dependent kinases (Cdk)
  2. cdk inhibitor proteins (CKI)
  3. protein phosphatases
  4. ubiquitin ligases and their regulators
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18
Q

What is the function of the cell-cycle control system?

A
  1. functions as a timer for the sequential events of the cell cycle
  2. the control system receives feedback, which can in turn influence progression into the next stage
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19
Q

Cell-cycle control system is a series of [ ]. Each switch [ ] initiates a specific event.

A
  1. binary (on/off) biochemical switches
  2. irreversibly
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20
Q

What are the three major regulatory transitions?

A
  1. start transition: late in G1 phase. Cell commits to chromosome duplication
  2. G2/M transition: promotes early steps of mitosis, leading to chromosome alignment in metaphase
  3. metaphase to anaphase transition: sister chromatid separation is initiated. Leads to mitosis and cytokinesis completion
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21
Q

If there is a problem completing DNA replication, the cell can be held in [ ] until problems are fixed.

A

G2/M transition

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22
Q

What is the function of Cdks?

A

as kinases, they phosphorylate proteins involved in initiation and regulation of cell cycle processes

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23
Q

Some Cdks phosphorylate proteins responsible for [ ] and [ ] of the nuclear envelope, which are needed for progression of mitosis.

A
  1. condensation
  2. breakdown
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24
Q

Cyclical activity of Cdks is determined by other regulator proteins known as [ ].

A

cyclins

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25
Q

What are the three major classes of cyclins?

A
  1. G1/S-Cyclins
  2. S-Cyclins
  3. M-Cyclins
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26
Q

The level of Cdks are [ ] throughout cell cycle.

A

constant

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27
Q

Although the level of Cdks are constant, cyclins are [ ] and [ ].

A

synthesized and degraded

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28
Q

If Cdks are not tightly bound to their associated cyclin, forming the [ ], their kinase activity is not carried out.

A

cyclin-Cdk complex

29
Q

[ ] can be delayed when the control system received feedback regardining incomplete [ ].

A
  1. M phase
  2. DNA replication
30
Q

What is the function of G1/S-Cyclins?

A

activate Cdks in late G1. Triggers progression of Start transition. Commits entry into vell cycle. Levels fall is S phase

31
Q

What is the function of S-Cyclins?

A

bind Cdks after Start transition. Stimulate chromosome replication, promote some early mitotic events. Levels remain elevated until mitosis

32
Q

What is the function of M-Cyclins?

A

activate Cdks that promote entry into mitosis at G2/M transition. Levels fall in mid-mitosis

33
Q

What is the function of G1-Cyclins?

A

help regulate the G1/S-Cyclins

34
Q

Extracellular signals stimulate cell division in part by increasing production of [ ].

A

G1-Cyclins

35
Q

Yeast cells have [ ] Cdk that binds [ ].

A
  1. one
  2. all types of cyclins
36
Q

Verbetrate cells have [ ] Cdks.

37
Q

What are the four Cdks in vertebrates?

A
  1. 2x interact with G1-cyclins
  2. 1x interacts with G1/S-cyclin and S-cyclins
  3. 1x interacts with S- and M- cyclins
38
Q

Cdk activation requires binding of cyclin and phosphorylation by the [ ].

A

Cdk-activating kinase (CAK)

39
Q

CAK activity is [ ] through the cell cycle.

40
Q

What is the function of Wee1?

A

phosphorylates at a second site, this decreasing Cdk activity

41
Q

What is the function of Cdc25 phosphatase?

A

increases Cdk activity by removing inhibitory phosphate groups

42
Q

G1/S-Cdks and S-Cdks are regulated by [ ].

A

Cdk inhibitor proteins (CKIs)

43
Q

What is the function of CKIs?

A

wrap around the cyclin-Cdk complex, inhibiting the active site

44
Q

Various [ ] can [ ] the effects of Cdks and other kinases.

A
  1. protein phosphatases
  2. reverse
45
Q

[ ] is a particularly important regulator of the cell cycle.

A

protein phosphatase 2A (PP2A)

46
Q

PP2A has [ ], with the form depending on the type of [ ].

A
  1. multiple forms
  2. regulatory subunit/B subunit
47
Q

What is the function of B subunit?

A

influences substrate specificity, localization, and regulation of the enzyme (most important of B55 and B56)

48
Q

Cdk and phosphatase activities are [ ] through the cell cycle.

A

coordinated

49
Q

PP2A-B55 is high during [ ], but inhibited during early [ ], when [ ] levels increase.

A
  1. interphase
  2. mitosis
  3. M-Cdk
50
Q

PP2A-B55 is active prior to [ ].

51
Q

What is the function of PP2A-B55?

A

reduces phosphorylation of M-Cdk targets

52
Q

M-Cdk activity increases at [ ]

A

beginning of mitosis

53
Q

One target of M-Cdk is a kinase called [ ]. [ ] then phoshorylates [ ].

A
  1. Great wall
  2. Great wall
  3. Ensa
54
Q

What is the function of Ensa?

A

binds PP2A-B55, inhibiting phosphatase activity

55
Q

In anaphase, M-Cdk decreases with the [ ].

A

degradation of cyclins

56
Q

What happens after the degradation of cyclins?

A

PP2A-B55 dephosphorylates Greatwall (blocks it’s own inhibitor)

57
Q

How are targets of Cdks targeted?

A

cyclins have binding site (in addition to Cdk-binding site) that can recognize specific Cdk substrates

58
Q

[ ] has specificity for proteins involved in DNA replication.

A

S-Cdk complex

59
Q

The [ ] may target [ ] throuh the cell cycle.

A
  1. same cyclin-Cdk complex
  2. different substrates
60
Q

[ ] substrates are targeted earlier, [ ] substrates are targeted later

A
  1. high-affinity
  2. low-affinity
61
Q

[ ] may play a role in determining the order of phosphorylation.

A

total enzyme activity

62
Q

M-Cdk levels [ ] in mitosis. [ ] levels of active enzyme would facilitate interaction with [ ].

A
  1. rise early
  2. increased
  3. lower-affinity substrates
63
Q

Switchlike Cell-Cycle transitions are achieved through [ ].

A

positive-feedback mechanisms

64
Q

How does Cdc25 initially activate?

A

external signal of some type leads to a small increase in Cdc25 activation.

65
Q

A different mechanism is used for the [ ] transition.

A

metaphase to anaphase

66
Q

Rather than kinase activity determining transition, [ ] is what facilitates the metaphase to anaphase transition

A

protein destruction

67
Q

What is the function of anaphase-promoting complex/ cyclosome (APC/C)?

A
  1. belongs to family of ubiquitin ligase enzymes
  2. ubuniquitin ligases are used to target specific proteins for destruction in proteasomes, which are large protein complexes that hydrolyze targeted proteins
68
Q

What are the two primary targets of APC/C?

A
  1. securin: destruction of securing in metaphase leads to separation of sister chromatids. This leads to anaphase
  2. S- and M-cyclins: inactivates most Cdks in the cell. As a result, Cdk targets become dephosphorylated by PPA2. Required for the completion of M phase

BISC 372 (7 decks)

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