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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

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?

A

Making the network of protein fibres (SPINDLE FIBRES)

25
Q

1st stage of the formation of mitotic spindle

A

Mitotic spindle fibres grab onto a protein complex called kinetochore which is attached to the centromere

26
Q

What is the mitotic spindle made by?

A

Spindle pole body

27
Q

What else happens before mitosis to the nuclear membrane?

A

It breaks down so the spindle has access to the chromosomes

28
Q

What happens to the kleisin when the cell segregates?

A

Degrades part of the kleisin subunit by cohesin

29
Q

2 things that happens when the sister chromatids have reached opposite poles of the cell

A

1) Nuclear membrane reforms
2) Cytoplasm divided in 2 by contractile ring of filaments composed of actin & myosin II

30
Q

What happens to the contractile ring in animal cells?

A

Divides the cytoplasm from the OUTSIDE IN

31
Q

What happens to the contractile ring in plant cells?

A

Contractile ring DOES NOT form
New cell wall is constructed between daughter nucleii, cytoplasm partitioned from INSIDE OUT

32
Q

What is new wall synthesis guided by?

A

Phragmoplast: structure that contains microtubules from mitotic spindle

33
Q

What does it mean when unicellular organisms operate a closed mitosis?

A

Don’t need to degrade nuclear membrane

34
Q

What does it mean when multicellular organisms operate a open mitosis?

A

Nuclear membrane breaks down & reforms

35
Q

What are stem cells attached to ?

A

Niche cell, which blocks their differentiation, but cell division is allowed

36
Q

What happens during polarity stem cell division?

A

1 daughter is released & free to differentiate, other daughter stays attached to the niche cell & remains a stem cell

37
Q

2 cell cycle control

A

1) Anchorage Dependence
2) Density-Dependent Inhibition

38
Q

Define anchorage dependence

A

Cells must be attached to a layer or substance in order to divide

39
Q

Define density-dependent inhibition

A

Once cells are in contact with each other, they stop dividing

40
Q

3 aspects of the cell cycle control system

A

1) Cell cycle engine
2) Co-ordination
3) Checkpoints

41
Q

Define cell cycle engine

A

Protein complex that drives the cell division in every eukaryote cell

42
Q

Define coordination in the cell cycle control system

A

Cell has to know where it is

43
Q

Define checkpoints in the cell cycle control system

A

Cycle will stop if the DNA is damaged

44
Q

2 proteins that drive the cell cycle engine

A

1) Cyclin
2) Cyclin dependent protein kinase (CDK)

45
Q

Why is cyclin key to regulating the cell cycle?

A

1) Undergo cycles of synthesis & degradation
2) Different CDK’s & cyclins, each pair activating different phase of the cell cycle

46
Q

What degrades cyclin?

A

Proteolysis

47
Q

Role of coordination referring to S phase, G1 and G2 phase cells

A

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
Q

Why does surveillance mechanisms (checkpoints) operate continually?

A

Ensure next phase is not initiated before the previous one is finished

49
Q

What is the restriction point checkpoint?

A

A positive signal from outside that instructs the cell to divide

50
Q

What is the checkpoint during mitosis?

A

Cell ask itself is DNA synthesis complete?

If NOT, cell cycle is frozen

51
Q

What is the checkpoint in M?

A

Spindle checkpoint

52
Q

What is the spindle checkpoint?

A

Cell ask itself, is each chromosome attached to the spindle?

If NO, cell cycle is suspended

53
Q

2 consequences of checkpoint failure

A

1) Failure of DNA damage checkpoint
2) Spindle checkpoint failure

54
Q

What is DNA damage checkpoint?

A

Operates throughout the cell cycle to make sure there is no DNA damage

55
Q

What cell cycle does cancer feature?

A

De-regulated cell cycle

56
Q
A

Cell Biology & Neuroscience (17 decks)

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