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Cell Biology & Neuroscience > L11: The Cell Cycle > Flashcards

L11: The Cell Cycle Flashcards

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1
Q

How do prokaryotes divide?

A

Binary Fission

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2
Q

4 purposes of the cell cycle

A

1) Copy the genome & partition the copies
2) Enable a multicellular organism to grow to adult size
3) Maintain the total cell no. of an adult organism
4) Replace lost/damaged cells

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3
Q

2 pathways of binary fission

A

1) Replication of DNA
2) Cytokinesis

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4
Q

Stages of binary fission

A

1) DNA attached to cytoplasmic membrane
2) Cell enlarges & DNA duplicates
3) Septum forms
4) Cell divides into 2, DNA partitioned into each cell
5) Cells separate

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5
Q

How many origin of replication do prokaryotes have?

A

Circular chromosome of prokaryotes has 1 origin (ori) of replication

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6
Q

3 stages of replication of DNA

A

1) Circular chromosome of prokaryotes has 1 origin (ori) of replication
2) 2 replication forks (RF) form at the origin
3) 2 identical copies of circular chromosome

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7
Q

What does it mean when replication is bidirectional?

A

Opposite directions

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8
Q

What forms during the early steps in bacterial cytokinesis?

A

Ring of a protein, FtsZ

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9
Q

Where is the FtsZ found?

A

On the inner surface of the cytoplasmic membrane

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10
Q

What does the paradox resolve?

A

All cells have DNA

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11
Q

What does multi-fork replication ensure?

A

At least 1 round of replication is finished before cytokinesis

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12
Q

Features of the eukaryotic cell cycle that proposes complications

A

1) Genome is composed of multiple linear chromosomes
2) Multicellularity
3) Numerous organelles (rER, sER, golgi etc.)

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13
Q

Characteristics of the eukaryotic cell cycle

A

1) DNA must be accurate
2) Replicated chromosomes must be accurately segregated

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14
Q

What happens during G1 ?

A

Growth phase

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15
Q

What happens during S phase?

A

DNA replication

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16
Q

What happens during G2 phase?

A

Cell prepares for mitosis

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17
Q

What is produced at the end of S phase?

A

Each replicated chromosome has a pair of identical sister chromatids

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18
Q

What can’t the sister chromatids do?

A

Separate from each other, or else bipolar attachment to the mitotic spindle would be difficult to happen

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19
Q

What protein complex is used to make sure sister chromatids do not separate?

A

Cohesin

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20
Q

2 events in the beginning of mitosis?

A

1st event: Chromosome condensation
2nd event: Formation of the mitotic spindle

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21
Q

1st stage of chromosome condensation

A

Interphase: Chromosomes are not visible

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22
Q

2nd stage of chromosome condensation

A

M phase begins; where chromosomes are condensed & become visible

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23
Q

Function of condensin

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A

Protein complex that encircles loops of DNA & compresses the sister chromatids to give a compact structure

24
Q

What happens at the end of G2 phase?

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A

Making the network of protein fibres (SPINDLE FIBRES)

25
1st stage of the formation of mitotic spindle
Mitotic spindle fibres grab onto a protein complex called kinetochore which is attached to the centromere
26
What is the mitotic spindle made by?
Spindle pole body
27
What else happens before mitosis to the nuclear membrane?
It breaks down so the spindle has access to the chromosomes
28
What happens to the kleisin when the cell segregates?
Degrades part of the kleisin subunit by cohesin
29
2 things that happens when the sister chromatids have reached opposite poles of the cell
1) Nuclear membrane reforms 2) Cytoplasm divided in 2 by contractile ring of filaments composed of actin & myosin II
30
What happens to the contractile ring in animal cells?
Divides the cytoplasm from the OUTSIDE IN
31
What happens to the contractile ring in plant cells?
Contractile ring DOES NOT form New cell wall is constructed between daughter nucleii, cytoplasm partitioned from INSIDE OUT
32
What is new wall synthesis guided by?
Phragmoplast: structure that contains microtubules from mitotic spindle
33
What does it mean when unicellular organisms operate a closed mitosis?
Don't need to degrade nuclear membrane
34
What does it mean when multicellular organisms operate a open mitosis?
Nuclear membrane breaks down & reforms
35
What are stem cells attached to ?
Niche cell, which blocks their differentiation, but cell division is allowed
36
What happens during polarity stem cell division?
1 daughter is released & free to differentiate, other daughter stays attached to the niche cell & remains a stem cell
37
2 cell cycle control
1) Anchorage Dependence 2) Density-Dependent Inhibition
38
Define anchorage dependence
Cells must be attached to a layer or substance in order to divide
39
Define density-dependent inhibition
Once cells are in contact with each other, they stop dividing
40
3 aspects of the cell cycle control system
1) Cell cycle engine 2) Co-ordination 3) Checkpoints
41
Define cell cycle engine
Protein complex that drives the cell division in every eukaryote cell
42
Define coordination in the cell cycle control system
Cell has to know where it is
43
Define checkpoints in the cell cycle control system
Cycle will stop if the DNA is damaged
44
2 proteins that drive the cell cycle engine
1) Cyclin 2) Cyclin dependent protein kinase (CDK)
45
Why is cyclin key to regulating the cell cycle?
1) Undergo cycles of synthesis & degradation 2) Different CDK's & cyclins, each pair activating different phase of the cell cycle
46
What degrades cyclin?
Proteolysis
47
Role of coordination referring to S phase, G1 and G2 phase cells
If S phase fuses with G1 cell, the G1 DNA will enter S phase If S phase fuses with G2 cell, the G2 DNA will NOT be forced to enter S phase
48
Why does surveillance mechanisms (checkpoints) operate continually?
Ensure next phase is not initiated before the previous one is finished
49
What is the restriction point checkpoint?
A positive signal from outside that instructs the cell to divide
50
What is the checkpoint during mitosis?
Cell ask itself is DNA synthesis complete? If NOT, cell cycle is frozen
51
What is the checkpoint in M?
Spindle checkpoint
52
What is the spindle checkpoint?
Cell ask itself, is each chromosome attached to the spindle? If NO, cell cycle is suspended
53
2 consequences of checkpoint failure
1) Failure of DNA damage checkpoint 2) Spindle checkpoint failure
54
What is DNA damage checkpoint?
Operates throughout the cell cycle to make sure there is no DNA damage
55
What cell cycle does cancer feature?
De-regulated cell cycle
56

Cell Biology & Neuroscience (18 decks)

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