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Cell Biology > Chapter 17 > Flashcards

Chapter 17 Flashcards

1
Q

What are the different phases in the cell cycle

A 
Interphase :
       G1 phase 
        S phase
        G2 phase
M phase 
       Mitosis
        Cytokinesis
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2
Q

What happens in the prophase ?

A

Condensation of chromosomes;

Centrosomes have duplicated and the mitotic spindles form

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3
Q

What are condensins

A

5- subunit protein complex that reassembles cohesion

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4
Q

What happens in prometaphase

A

Nuclear envelop breaks down; spindles connect to chromosomes by their kinetochores and begin movement

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5
Q

What triggers the formation of the mitotic spindle

A

M-Cdk

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6
Q

What happens in meta phase

A

Chromosomes align at equator of each spindle pole by way of the microtubules of the mitotic spindle

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7
Q

What happens in anaphase

A

The sister chromatids separate to form daughter chromosomes that are pulled apart towards the spindle pole microtubules shorten and pokes move more apart

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8
Q

What happens in telophase

A

The daughter chromosomes decondense ; nuclear envelope reassembles ; contractile ring begins to contract

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9
Q

What happens in cytokinesis

A

Nuclear envelop surrounds chromosomes

Contractile ring has created cleavage furrow and cytoplasm is divided in two

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10
Q

This acts as a microtubule organizing center

A

Centrosomes

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11
Q

When does the duplication of the centrosomes begin and complete

A

S-phase

G2

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12
Q

Which protein help keeps the poles apart

A

Kinesin-5

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13
Q

Which proteins pulls poles toward each other

A

Kinesin-14

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14
Q

These proteins pushed chromosomes away from poles

A

Kinesin-4

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15
Q

These proteins keep spindle poles away from each other and near cortex

A

Dyneins

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16
Q

What is the arrangement of the sister kinetochores

A

Back - back

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17
Q

What protein helps remove cohesions in anaphase

A

Separase

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18
Q

What activated separase

A

Anaphase promoting complex

APC/C

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19
Q

What is an active anaphase promoting complex reffered as

A

Ubiquitin ligase

Degraded proteins like M-Cdk

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20
Q

What keeps separase inactive

A

Securin

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21
Q

How does the separase become active to remove cohesions

A

When APC/C becomes active it adds ubiquitin to securin which targets it for degradation which will allow separase to become active and will then degrade the cohesion of the sister chromatids

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22
Q

What happens in anaphase A

A

Sister chromatids separate

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23
Q

What happens in anaphase B

A

Spindle pokes move away from each other

24
Q

What is the contractile ring made of

A

Actin and myosin Filaments

25
Q

What allows the formation of parallel actin bundles in the contractile ring

A

Formin

26
Q

What needs to be activated in order for the contractile ring to assemble and contract

A

RhoA

27
Q

Name the phases of the cell cycle

A

G1
S phase
G2 phase
M phase

28
Q

What gives the cell cycle its quality control feature

A

Various checkpoints
G1/S -
G2/M
Metaphase ti anaphase

29
Q

What mediates the transition from one phase to another in the cell cycle

A

By cyclins and

Cyclin dependent kinases ( Cdk)

30
Q

When is Cdk active

A

When bound to cyclin

31
Q

Will progression of phases continue if Cdk is active

A

No

32
Q

The expression of this changes with the stages of the cell cycle

A

Cyclin

33
Q

How is the Cdk activated by cyclins

A

When cyclin is not present Cdks active site is blocked by a loop
When cyclin is bound to Cdk the loop is removed and activated Cdk

34
Q

When Cdk is active in the G1/S - G2/M phase what does it do to various proteins

A

Phosphorylates them so that the cell cycle progresses

35
Q

In comparison with the progression of the G1/S -G2/M stage what is the different in the metaphase to anaphase progression

A

Metaphase to ananphase progression requires degradation not phosphorylation

36
Q

What promotes the replication of DNA only once during the cell cycle

A

S-Cdk

37
Q

How are the sister chromatids held together after the DNA has been replicated

A

Cohesions

38
Q

What is the name of the stage in the cell cycle where cell divides in 2 daughter cells

A

Mitosis

39
Q

What mediates crossing over

A

Synaptomenal complex

40
Q

What happens in meiosis I

A

Homologous chromosomes pair together

Non sister chromatids exchange genetic material ( crossing over )

41
Q

What is one difference from meiosis I and meiosis II

A

In meiosis I it is the separation of the homologous chromosomes
In meiosis II it’s separation of sister chromatids

42
Q

Nondisjunctuon

A

Phenomenon that when homologs fail to separate properly

Some haploid gametes have more copies of chromosomes while others lack chromosome

43
Q

What are extracellular factors that influence cell growth and division

A

Mitogens
Growth factors
Survival factors

44
Q

What do mitogens do

A

Promote cell division
They activate Ras and MAP kinase pathway
Triggers G1- Cdk and S -Cdk to activate

45
Q

In what phase does chromosome duplication occur

A

S Phase

(DNA ) synthesis

46
Q

In what phase of the cell cycle does chromosome segregation and cell division occur

A

M-Phase

47
Q

What is the mitotic spindle

A

Giant bipolar array of microtubules

48
Q

G1, S, G2 are together called

A

Interphase

49
Q

Which phase requires the most time

A

Interphase

50
Q

Why are the gap phases G1 and G2 important

A

Provides time for the cell to monitor the internal and external environment to ensure conditions are suitable to proceed to S phase and mitosis

51
Q

What what are two components of the cell cycle control system

A

Cyclin

Cyclin dependent protein kinase ( Cdk)

52
Q

What helps the cyclin Cdk complex become fully activated

A

CAK
Cdk- activating kinase
It phosphorylates an amino acid near the entrance of the Cdk active site

53
Q

What is the key regulator of the metaphase to anaphase transition

A

APC/ C
(Anaphase promoting complex
Cyclosome)

54
Q

What are the two proteins that APC/C target for destruction

A

Securins - hold sister chromatids together

S- and M- cyclin s - inactivated most Cdks in the cell

55
Q

How does cyclin activate Cdk

A

It binds causing a loop to move away from the active site

56
Q

What type of enzyme is APC/C

A

Ubiquitin ligase

57
Q

What inactivates cyclin Cdk complexes in

A

CkIs ( Cdk inhibitor proteins

Cell Biology (10 decks)

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