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MBC > Cell replication > Flashcards

Cell replication Flashcards

1
Q

What are the proteins involved in the formation of cytoskeleton elements?

A

Actin filaments
Intermediate filaments
and microtubules (tubulins)

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2
Q

What are the roles of an intracellular cytoskeleton?

A 
Maintains cell shape and structure
Transportation of organelles
Cellular division (kinetochore fibers and spindle contraction
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3
Q

What proteins comprise microtubules?

A

Alpha and beta tubulins

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4
Q

How are tubulins arranged in microtubules?

A

Helical configuration

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5
Q

Why is the helical configuration important in microtubules?

A

Enables the expansion and development of microtubules, additional tubules can be added or subsequently removed

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6
Q

Where do microtubules originate from

A

Microtubules originate from the microtubule organising centres

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7
Q

What major protein comprises microfilaments?

A

Actin

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8
Q

What are the functions of microfilaments?

A

Proteins assist with the motility of organelles and cell

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9
Q

How are cilia and flagella arranged?

A

9 + 2 configuration

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10
Q

How do microtubules assist with the movement of organelles?

A

Microtubules are associated with motor proteins

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11
Q

What is aneuploidy?

A

An abnormal number of chromosomes

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12
Q

In cancer cells, how is cell division unregulated?

A

Contact inhibition of growth does not occur, as tumor cells do not recognize adjacent cells thereby resulting in the continued proliferation of cancer cells

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13
Q

What are the stages of the cell cycle?

A

Interphase, mitosis, cytokinesis

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14
Q

What are examples of nuclear division?

A

Mitosis and meiosis

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15
Q

What is cell division?

A

Cell division involves the separation of cytoplasmic contents (cytokinesis) M phase

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16
Q

What is G1?

A

The chromosomes form long uncondensed threads wound onto histone, cell is metabolically active.
Protein synthesis occurs
Organelle production
Cytoplasmic volume increases

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17
Q

What is the structure of the chromosome within the G-phase?

A

The chromosomes present are uncondensed

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18
Q

Which proteins are associated with chromosomes?

A

Histone proteins

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19
Q

What occurs during the S-phase?

A

S phase is referred to as the synthesis phase whereby semi-conservative replication occurs within the nucleus/.
Histones are synthesised and attached to DNA
organelle synthesis: Mitochondria, centromere, golgi apparatus

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20
Q

How are chromosomes structured within the S-phase?

A

Chromosomes are condensed and visible as sister chromatids attached to the centromere

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21
Q

When is replicated DNA checked for errors and corrected?

A

G2 phase

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22
Q

Which phase during the cell cycle in which spindle proteins are produced?

A

G2 phase

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23
Q

What is M-phase?

A

Mitosis (nuclear division) and cytokinesis

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24
Q

When is mitosis most vulnerable?

A

Irradiation, heat shock chemicals
DNA Damage cannot be repaired
Gene transcription silenced

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25
Q

When is the decision point?

A

G1

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26
Q

When is the second decision point?

A

G2

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27
Q

What is the structure of centrioles?

A

Small hollow cylinders made of microtubules, made from the globular protein tubulin

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28
Q

Describe how centrioles arranged?

A

Pairs at right angles to each other, forming a centrosome

Composed of 9 triplets of microtubules

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29
Q

What is a centrosome?

A

Mother and daughter centriole pair

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30
Q

What is the function of a centriole?

A

Involved in the separation of chromosomes during cell division; producing a spindle

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31
Q

Which centriole do microtubules project from?

A

Elongate from mother centriole

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32
Q

What is chromatin?

A

The complex of DNA & Protein

33
Q

What are the stages of mitosis?

A

Prophase
Metaphase
Anaphase
Telophase

34
Q

What occurs during prophase 1?

A

Chromosome condensation occurs, chromosomes become visible as sister chromatids attached by the centromere and associated with kinetochore fibres

35
Q

What occurs during prophase II?

A

Spindle formation, duplicated centrosomes migrate to opposite poles of the nucleus, organize
Assembly of spindle microtubules
Asters form, radial microtubule array

36
Q

Where do the radial arrays meet?

A

The radial arrays form a collection of polar microtubules at the spindle equator, collectively forming the spindle

37
Q

What state are microtubules in?

A

Dynamic state

38
Q

What is a dynamic state?

A

Constant arrangement and addition of tubulin molecules (polymerization and depolymerisation)

39
Q

What occurs during prometaphase-I?

A

Nuclear envelope breaks down, releasing chromatids into the cytoplasm
Nucleolus disappears,
Spindle formation mainly complete

40
Q

What is the role of kinetochore fibers?

A

Project from the centromere, interact with spindle microtubules, attachment of chromosomes to the spindle

41
Q

What occurs during metaphase?

A

Microtubules from the opposite pole is captured by sister kinetochore.
Contraction of spindle cause chromosomes to translocate towards the centre (spindle equator)

42
Q

What is CENP-E?

A

Centromere protein E (Kinetochore tension sensing)

43
Q

What occurs during anaphase?

A

Centromeres split, separating each sister chromatid
Spindle contracts, pulling the chromatids centromere first towards the opposite pole
Movement of chromatids caused by overlapping spindle fibres sliding past each other
Spindle fibres lengthen and shorten depending on addition/removal of tubulin molecules
ATP is used

44
Q

What protein holds the sister chromatids together, and is subsequently broken down during anaphase?

A

Cohesin

45
Q

What occurs during Anaphase-A?

A

Breakdown of cohesin, microtubules get shorter, and daughter chromosomes pulled towards opposite spindle poles

46
Q

What occurs during Anaphase-B?

A

Daughter chromosomes migrate to poles, spindle poles migrate apart

47
Q

What process occurs during telophase?

A

New nuclear envelope develops around the group of chromatids
Formation fo two identical daughter nuclei
Chromatids uncoil and lengthen into chromosomes
Spindle fibers disintegrate, and formation of the nucleolus
A contractile ring of actin and myosin filaments assembled

48
Q

What happens to the chromatids during telophase?

A

Uncoil and lengthen, nucleolus reforms

49
Q

What proceeds from telophase?

A

Cytokinesis occurs, division of cytoplasm

50
Q

What forms at the equator of the cell during cytokinesis?

A

Cleavage furrow

51
Q

How does the cleavage furrow split the cells into two?

A

Contractile ring

52
Q

What are spindle assembly checkpoints?

A

Monitors the status of chromosome microtubule attachments, delays the onset of anaphase until the kinetochores have formed stable bipolar connections with the mitotic spindle

53
Q

How do kinetochore fibres attach to the mitotic spindle?

A

Form stable bipolar connections

54
Q

What protein comprises kinetochore fibres?

A

Centromere protein E (CENP-E)

BUB protein kinases bind onto kinetochore and dissociate once chromosomes are properly attached

55
Q

Which kinases detects the correct attachment of chromatids to spindles?

A

BUB protein kinases

56
Q

What is aneuploidy?

A

The mis-attachment of microtubules to kinetochore fibres resulting in abnormal number of chromosomes

57
Q

Why does aneuploidy occur?

A

Defects in the mitotic spindle checkpoint facilitate tumorigenesis

58
Q

Why does aberrant division occur?

A

Multipolar spindles, defects in chromosome cohesion, spindle attachment defects
Impairment in spindle checkpoint

59
Q

What is a cell-cycle arrest?

A

Stopping point within the cell cycle no longer involved in duplication or replication
Cell cycle checkpoints are control mechanisms that regulate proper cellular division
Including DNA damage and insufficient cell size

60
Q

What is apoptosis?

A

Programmed cell death

61
Q

What enzymes initiate apoptosis?

A

Initiator caspases

62
Q

What phase do cells enter due to the absence of stimulus?

A

G0-Quiescent phase

63
Q

Which phase are differentiated phase predominantly in?

A

G0 (cell isn’t dividing)

64
Q

What is the signaling cascade initial step?

A

Extracellular growth factor ligand binds to GF receptor,

65
Q

What occurs after growth factor ligand binding to GF receptor?

A

Receptors pair up and behave as kinases, phosphate groups to intracellular molecules. Kinases RAF is activated
RAF phosphorylates and activates MEK
MEK phosphorylates ERKs

66
Q

What is MEK?

A

Mitogen activated protein kinase

67
Q

What are ERKs?

A

Extracellular regulated kinases

68
Q

What do ERKs do?

A

Phosphorylate and activate variety of target molecules, transcription factors (C-myc)

69
Q

What is C-myc? What does it do?

A

Transcription factor. Drives the cell forward into S phase

70
Q

What is the RAF-MEK-ERK pathway?

A

Mitogen activated protein kinase cascade. The MAP kinase enzymes increase protein synthesis and decrease protein degradation allowing the cell to double in size

71
Q

What is a mitogen?

A

The signal that causes a cell to undergo mitosis or divide

Promotes the transition of G0 to G1

72
Q

What is a CDK? What do they do?

A

A cyclin-dependent kinase allows the sequence of cell cycle events to be controlled

Only active when cyclin is bound

73
Q

Note

A

Remember, different cells divide at different rates

74
Q

What cells don’t divide?

A

Cardiac myocytes and neurons

75
Q

How and why do cells leave G0?

A

Signalling cascade occurs where cell responds to extracellular factors

Signals from growth factors are amplified and together with other pathways (map kinase pathway) leads to cell growth

Growth factors stimulate entry from G0 to G1

76
Q

In CDK activity, what is the key role of cyclin?

A

Cyclin concentration is cyclic. So it is produced and it is degraded

Active mitosis only happens when CDK and cyclin are together

77
Q

How are CDKs activated? What is involved?

A

Through sequential phosphorylation and dephosphorylation

Kinases phosphorylate it and phosphatase remove phosphates

78
Q

What is retinoblastoma?

A

Acts as a brake on cell proliferation

It binds to a transcription factor (TF), holding it in its inactive form (mainly E2F TF-turn on things needed for s phase like DNA polymerase)

Means TDs can’t turn on genes needed for cell cycle progression

MBC (4 decks)

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