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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
What are the three major classes of cyclins?
1. G1/S-Cyclins 2. S-Cyclins 3. M-Cyclins
26
The level of Cdks are [ ] throughout cell cycle.
constant
27
Although the level of Cdks are constant, cyclins are [ ] and [ ].
synthesized and degraded
28
If Cdks are not tightly bound to their associated cyclin, forming the [ ], their kinase activity is not carried out.
cyclin-Cdk complex
29
[ ] can be delayed when the control system received feedback regardining incomplete [ ].
1. M phase 2. DNA replication
30
What is the function of G1/S-Cyclins?
activate Cdks in late G1. Triggers progression of Start transition. Commits entry into vell cycle. Levels fall is S phase
31
What is the function of S-Cyclins?
bind Cdks after Start transition. Stimulate chromosome replication, promote some early mitotic events. Levels remain elevated until mitosis
32
What is the function of M-Cyclins?
activate Cdks that promote entry into mitosis at G2/M transition. Levels fall in mid-mitosis
33
What is the function of G1-Cyclins?
help regulate the G1/S-Cyclins
34
Extracellular signals stimulate cell division in part by increasing production of [ ].
G1-Cyclins
35
Yeast cells have [ ] Cdk that binds [ ].
1. one 2. all types of cyclins
36
Verbetrate cells have [ ] Cdks.
four
37
What are the four Cdks in vertebrates?
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
Cdk activation requires binding of cyclin and phosphorylation by the [ ].
Cdk-activating kinase (CAK)
39
CAK activity is [ ] through the cell cycle.
constant
40
What is the function of Wee1?
phosphorylates at a second site, this decreasing Cdk activity
41
What is the function of Cdc25 phosphatase?
increases Cdk activity by removing inhibitory phosphate groups
42
G1/S-Cdks and S-Cdks are regulated by [ ].
Cdk inhibitor proteins (CKIs)
43
What is the function of CKIs?
wrap around the cyclin-Cdk complex, inhibiting the active site
44
Various [ ] can [ ] the effects of Cdks and other kinases.
1. protein phosphatases 2. reverse
45
[ ] is a particularly important regulator of the cell cycle.
protein phosphatase 2A (PP2A)
46
PP2A has [ ], with the form depending on the type of [ ].
1. multiple forms 2. regulatory subunit/B subunit
47
What is the function of B subunit?
influences substrate specificity, localization, and regulation of the enzyme (most important of B55 and B56)
48
Cdk and phosphatase activities are [ ] through the cell cycle.
coordinated
49
PP2A-B55 is high during [ ], but inhibited during early [ ], when [ ] levels increase.
1. interphase 2. mitosis 3. M-Cdk
50
PP2A-B55 is active prior to [ ].
mitosis
51
What is the function of PP2A-B55?
reduces phosphorylation of M-Cdk targets
52
M-Cdk activity increases at [ ]
beginning of mitosis
53
One target of M-Cdk is a kinase called [ ]. [ ] then phoshorylates [ ].
1. Great wall 2. Great wall 3. Ensa
54
What is the function of Ensa?
binds PP2A-B55, inhibiting phosphatase activity
55
In anaphase, M-Cdk decreases with the [ ].
degradation of cyclins
56
What happens after the degradation of cyclins?
PP2A-B55 dephosphorylates Greatwall (blocks it's own inhibitor)
57
How are targets of Cdks targeted?
cyclins have binding site (in addition to Cdk-binding site) that can recognize specific Cdk substrates
58
[ ] has specificity for proteins involved in DNA replication.
S-Cdk complex
59
The [ ] may target [ ] throuh the cell cycle.
1. same cyclin-Cdk complex 2. different substrates
60
[ ] substrates are targeted earlier, [ ] substrates are targeted later
1. high-affinity 2. low-affinity
61
[ ] may play a role in determining the order of phosphorylation.
total enzyme activity
62
M-Cdk levels [ ] in mitosis. [ ] levels of active enzyme would facilitate interaction with [ ].
1. rise early 2. increased 3. lower-affinity substrates
63
Switchlike Cell-Cycle transitions are achieved through [ ].
positive-feedback mechanisms
64
How does Cdc25 initially activate?
external signal of some type leads to a small increase in Cdc25 activation.
65
A different mechanism is used for the [ ] transition.
metaphase to anaphase
66
Rather than kinase activity determining transition, [ ] is what facilitates the metaphase to anaphase transition
protein destruction
67
What is the function of anaphase-promoting complex/ cyclosome (APC/C)?
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
What are the two primary targets of APC/C?
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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