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SBO > Chapter 12: The Cell Cycle > Flashcards

Chapter 12: The Cell Cycle Flashcards

1
Q

Stages of cell cycle

A

G1 (first gap), S (synthesis), G2 (second gap), M (mitotic)

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2
Q

Main event during S phase

A

DNA replication

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3
Q

Main event during G2 phase

A

Centrosome duplication

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4
Q

Mitotic spindle consists of

A

Fibers made out of microtubules (some from cytoskeleton)

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5
Q

Microtubules are made up of

A

a- and B- tubulin dimers (proteins)

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6
Q

Centrosome

A
  • Microtubule-organising centre (MTOC)
  • Where the pair of centrioles is located
  • Where assembly of spindle microtubules start
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7
Q

What happens during prophase?

A
  • mitotic spindle begins to form

- centrosomes move away from each other (partly due to lengthening MTs)

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8
Q

By the end of prometaphase, Centrosomes are

A

At opposite poles of the cell

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9
Q

The spindle includes

A

Two centrosomes, spindle MTs, and two asters

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10
Q

Spindle MTs attach to kinetochores during

A

Prometaphase

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11
Q

Metaphase plate

A

An imaginary plate in the middle of the cell on which centromeres are aligned on

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12
Q

What happens during prometaphase? (3)

A
  • Nuclear envelope disintegrates
  • Kinetochore MTs attach to kinetochores
  • Non-KT MTS interact and overlap
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13
Q

What happens during metaphase? (3)

A
  • centrosomes are at opposite poles of the cell
  • Chromosomes are aligned at the metaphase plate
  • MTs of Asters have grown and are attached to the plasma membrane
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14
Q

Aster

A

A radial array of short MTs extending from each centrosome

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15
Q

Separase

A

An enzyme that cleaves cohesins holding sister chromatids together

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16
Q

Two mechanisms for sister chromatid movement:

A

1) Depolymerisation of microtubules at kinetochore ends after passing through motor proteins
2) Depolymerisation at the poles as motor proteins “reel chromosomes in”

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17
Q

Function of nonkinetochore microtubules during anaphase

A

Elongate the cell

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18
Q

In which phases can microtubules lengthen?

A

Prophase and anaphase (non-kinetochore)

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19
Q

What is on the cytoplasmic side of the cleavage furrow?

A

Contractile ring of actin microfilaments associated with myosin

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20
Q

Traditional drawstring model

A

Myosin causes antiparallel actin to slide past each other

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21
Q

Where do vesicles containing cell plate material come from?

A

Golgi apparatus

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22
Q

How do animal and plant cells undergo cytokinesis?

A

Animal: Cleavage furrow
Plant: Cell plate

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23
Q

Describe binary fission.

A

Cell division in prokaryotes, where cell grows to double its size and divides into two

24
Q

How many origins of replication on E.coli?

A

2

25
Q

How does one copy of the origin move to the opposite pole of the cell?

A

Polymerisation of actin-like protein

26
Q

Roles of tubulin in eukaryotic VS prokaryotic cells

A

Forming microtubules VS cytokinesis

27
Q

How does the tubulin-like protein help split the prokaryotic cell into two?

A

It pinches the plasma membrane inward

28
Q

Division in Dinoflagellates (nuclear envelope, microtubules, chromosomes)

A
  • nuclear envelope intact
  • chromosomes attached to n.e.
  • microtubules pass thru nucleus in cytoplasmic tunnels
  • division like binary fission
29
Q

Division in diatoms and some yeasts (nuclear envelope, microtubules, chromosomes) ,

A
  • nuclear envelope intact
  • spindle within the nucleus
  • chromosomes pulled apart by microtubules
30
Q

Division in most eukaryotes (nuclear envelope, microtubules, chromosomes)

A
  • nuclear envelopes break down
  • spindle forms outside nucleus
  • microtubules pull apart chromosomes
31
Q

Division in bacteria

A
  • no nucleus (membrane-bound organelle)
  • circular DNA
  • origins of replication
  • no microtubules
32
Q

Important checkpoints in cell cycle

A

G1, G2, M

33
Q

Concentration of protein Kinases

A

Stays constant

34
Q

Concentration of cyclin

A

Rises during S and G2 phases, falls abruptly during M phase

35
Q

Go-ahead signal at G2 checkpoint

A

Cyclin-Cdk complex

36
Q

Function of MPF

A

1) Phosphorylation of various proteins of nuclear lamina
2) chromosome condensation
3) spindle formation

37
Q

Mechanism of switching off MPF

A

Destruction of cyclin during anaphase

38
Q

Concentration of MDF

A

Rises and falls during M phase

39
Q

Presence VS absence of go-ahead signal at G1 checkpoint

A

usually completes G1-M phases
VS
switches to G0 phase (non-dividing)

40
Q

Go-ahead signal for Anaphase to occur

A

All sister chromatids are attached to spindle fibres

41
Q

Regulatory molecule during anaphase

A

Protein complex

42
Q

Outline the reasons for uncontrolled cell division in cancer cells (7)

A

1) Lack of density-dependent inhibition and anchorage dependence
2) Growth factors in culture medium not needed for growth
3) Faulty cell cycle control
4) Cells stop dividing at random points in the cycle, rather than at normal checkpoints
5) Can divide indefinitely with enough nutrients
6) Has telomerase, which functions to maintain telomere length and prevent cell from undergoing replicative cell senescence/apoptosis 7)Evade apoptosis when mistake has occurred (e.g. during DNA replication)

43
Q

Growth factor

A

Protein released by cells that stimulate other cells to divide

44
Q

Why do cancer cells not need growth factors in the culture medium?

A

1) self-produce growth factors
2) Absence of growth factor does not affect signal received by cell cycle control system (i.e. abnormality in signalling pathway)

45
Q

Reason for faulty cell cycle controls

A

Mutation leading to alteration of protein products

46
Q

Transformation [process; definition]

A

Process that causes cells to behave like cancer cells (i.e. divide indefinitely)

47
Q

Platelet-derived growth factor (PDGF)

A

Triggers division of cultured fibroblasts

48
Q

How is signal transduction pathway triggered?

A

Binding of PDGF molecules to receptors on fibroblasts

49
Q

Cancer cells do not exhibit

A

Anchorage dependence or density dependent inhibition

50
Q

Benign tumor VS cancerous tumor

A

Remains at original site
VS
Spreads to new tissues and organs

50
Q

How do cancer cells undergo Metastasis? (spread of cancer cells to distal organs) (2)

A

1) Loss of attachment to neighbouring cells and extracellular matrix
2) Signalling molecules that cause blood vessels to grow towards tumor

52
Q

Definition and Effect of Taxol (drug)

A

Chemotherapeutic drug that stops anaphase by preventing microtubule depolymerisation, thus leading to the cell’s destruction

53
Q

State the two types of Cancer Treatment.

A
  1. Localised tumors: Radiation therapy

2. Metastatic tumors: chemotherapy—drugs toxic to actively dividing cells circulated in the blood

54
Q

Mechanism of radiation therapy

A

Damages DNA in cancer cells more so than normal cells, as they do not have the ability to repair damaged DNA

55
Q

Side effect of chemotherapy (+examples)

A

Affects normal cells that divide often; e.g. nausea → intestinal cells, hair loss → hair follicle cells, reduced immunity → immune system cells

56
Q

Outline the changes observed in cells of malignant tumors, (5)

A

1) excessive proliferation
2) unusual no. Of chromosomes (May/may not be due to transformation)
3) Altered metabolism
4) Loss of cell-cell adhesion and attachment to extracellular matrix, thus can spread into nearby tissues
5) Secretion of signalling molecules that cause blood vessels to grow towards tumor

SBO (3 decks)

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