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The cell cycle Flashcards

1
Q

How do prokaryotes divide?

A

Asexual reproduction - Binary Fission

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2
Q

How do eukaryotes divide?

A

Mitosis or meiosis

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3
Q

How does binary fission differ from mitosis?

A

Because prokaryotic cells do not have a true nucleus like eukaryotes

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4
Q

How does mitosis differ from binary fission?

A

There is no mitotic spindle formation in the nucleus during binary fission.

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5
Q

What does meiosis produce?

A

23 pairs of chromosomes -> haploid gametes
(1 chromatid from each of the 46 chromosomes)

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6
Q

What is the result of the cell cycle?

A

2 genetically identical daughter cells

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7
Q

How long do cells spend in interphase?

A

90-95%

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8
Q

What are the two main phases of the cell cycle?

A

Interphase and Mitosis

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9
Q

What are the three stages of interphase?

A

G1, S and G2

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10
Q

Why is the cell cycle important?

A
  • Healing and tissue repair
  • Growth
  • Replacement
  • Reproduction
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11
Q

What are the three doubles of interphase?

A
  1. Double cell content
  2. Double chromosomes
  3. Double check
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12
Q

What happens during G1 Phase?

A

Cellular contents (excluding chromosomes) are duplicated

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13
Q

What happens during S phase?

A

DNA replication occurs which aims to duplicate all chromosomes to get a complete extra set of all genetic material.

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14
Q

What happens during G2 phase?

A

The cell prepares for division by organising and condensing material. It doubles checks and repairs duplicated genetic material.

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15
Q

In the cell cycle, what is progress through phases dependent on?

A

Cellular checkpoints

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16
Q

What happens after Interphase?

A

Mitosis

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17
Q

What are the four main stages of mitosis?

A

Prophase, Metaphase, Anaphase and Telophase

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18
Q

What happens to each daughter cell?

A

Each daughter cell then enters their own interphase and then the cell cycle begins again

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19
Q

What happens at the end of telophase and why?

A

Cytokinesis occurs which enables the distribution and separation of all components into two identical daughter cells.

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20
Q

What happens during prophase?

A

Spindle fibres appear
Chromosomes condense

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21
Q

What happens during prometaphase?

A

Spindle fibres attach to chromosomes
Chromosomes condense

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22
Q

What happens during metaphase?

A

Chromosomes align

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23
Q

What happens during anaphase?

A

Centromeres divide
Sister chromatids move to opposite poles

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24
Q

What happens during telophase?

A

Nuclear membrane reforms
Chromosomes decondense
Spindle fibres disappear

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25
What happens during cytokinesis?
Cytoplasm divides Parent cell becomes 2 daughter cells with identical genetic information
26
What is G0 phase?
G0 phase is a state of cell cycle arrest which happens after mitosis is completed if there are no external growth stimuli
27
What are the states of G0 phase
Reversible (quiescent)) Irreversible (senescent and differentiated)
28
Tell me about the reversible G0 phase. (examples)
It is regulated by extrinsic signals Examples: tissue stem cells, hepatocytes
29
Tell me about the irreversible G0 phase. (examples)
Senescent - DNA damage/telomere shortening - Cell no longer viable to continue dividing Differentiated - bone/nerve/muscle
30
What state are the majority of cells with DNA content in adults in?
G0 phase
31
Why are control mechanisms important?
To ensure safe and proper progression
32
What do checkpoints have the capability of doing?
Terminating the cell cycle
33
What are the three main checkpoints?
G1 checkpoint G2/M checkpoint Spindle checkpoint (metaphase - anaphase)
34
What can induce activation of cyclins/CDKs?
Mitogenic signals like hormones and growth factors
35
What are the key regulators of checkpoints and responsible for progression?
Heterodimers composed of cyclins and cyclindepdendent kinases (CDKs)
36
What can cause the activation of catalytic subunit CDKs?
Binding of the regulatory subunit of cyclins to the catalytic subunit (CDKs)
37
How do heterodimers consecutively orchestrate the entry into the next cell cycle phase?
After the binding of the regulatory subunit to the catalytic subunit they then phosphorylate proteins which leads to te next cell cycle phase
38
What cyclins and CDKs are used in G1 phase?
Cyclin D and CDK 4/6
39
What cyclin and CDK are used in G1/s phases?
Cyclin E and CDK 2
40
What cyclin and CDKs are used in the s phase?
Cyclin A and CDK 2
41
What cyclin and CDKs are used in G2/M?
Cyclin B and CDK1
42
What is the main reason the cell cycle would stop at the G1/S and G2/M checkpoints?
DNA damage
43
What are key proteins in determining outcome of G1 checkpoint?
E2F family and Rb
44
What is the mechanism behind the G1 checkpoint?
DNA damage increases degradation of Cyclin D
45
What is the point of the G1 checkpoint?
It is the point of commitment to entering cell cycle (enter G0, delay or proceed)
46
What happens at G1/S checkpoint?
It hyperphosphorylates Rb at all sites causing complete inactivation
47
What stops backwards movement at the G1/S checkpoint?
The transcription of Cyclin A
48
Why is G2/M checkpoint a safety net before mitosis?
It prevents DNA damage/mutations continuing and being replicated and being passed on.
49
What does the G2/M checkpoint require?
G2 requires a DNA damage assessment
50
What is the mechanism of G2/M progression?
Protein accumulation and Wee1 inhibited causing the activation of CyclinB/CDK1
51
What acts as DNA sensors in the G2/M checkpoint?
ATR and ATM
52
What is the similarity between G1/S and G2/M?
subsequent similar mechanisms including the activation of p53
53
What happens if DNA damage is detected?
The cell cycle is halted or damaged
54
What are the two types of mechanism if DNA damage is detected?
Rapid and prolonged
55
Explain rapid mechanism if DNA damage is detected?
Proteins ATM and ATR act as sensors These activates Chk2 and Chk1 causing the inhibition of CyclinE/Cdk2 Therefore cells does not progress
56
Explain prolonged mechanism if DNA damage is detected?
P53 is activated -> Cyclin E/CDK2 P21 -> Rb dephosporylation -> inhibits G1/S transition
57
What causes cancer?
Loss of function Damaged DNA is replicated Cancer
58
When does the mitotic spindle checkpoint occur?
In metaphase
59
What needs to happen to the chromosomes during metaphase checkpoint?
Chromosomes need to have aligned and be under tension
60
What detects the tension during metaphase checkpoint?
APC (anaphase-promoting complex)
61
What does the activation APC/C during the metaphase checkpoint do?
Cause the cycle to move onto anaphase
62
What causes metaphase checkpoint to continue?
Equal distribution of chromosomes between new daughter cells
63
What causes the G1/S checkpoint to continue?
Sufficient number of organelles Growth factors activation
63
What causes G2/M checkpoint to continue?
Completely replicated genome Large Cell volume
64
What causes metaphase checkpoint to fail?
Chromatids are not properly assembled on mitotic spindle
65
What does a change in base cause?
A change in the function of a protein
66
What codes protein?
RNA
67
What do chromosomes contain?
DNA
68
What is DNA composed of?
Bases
69
What do sequence of bases code?
Exons and introns
70
What codes genes?
Exons
71
Why do introns not code genes?
They are non coding and are spliced/removed
72
Do proteins work alone or in combination?
Trick question: Both
73
How many exons in the human genome?
234,000
74
How can multiple proteins come from a single gene?
Because introns allow alternative splicing causing multiple proteins from a single gene.
75
What are the four common causes of DNA damage?
Base mismatch Single-strand break Double strand break Bulky adducts
76
What external factors cause base mismatch DNA damage?
DNA replication stress
77
What external factors cause single strand break DNA damage?
Oxygen radicals Ionising radiation Chemotherapeutic
78
What external factor cause double strand break DNA damage?
Ionizing radiation Chemotherapeutic
79
What external factors cause bulky adducts DNA damage?
Ultraviolet light Polycyclic aromatic hydrocarbons
80
What happens to the DNA during base mismatch?
Insertions/deletions
81
What happens to the DNA during double strand break?
Interstrand crosslinks
82
What happens to the DNA during Bulky adducts?
Interstrand crosslinks
83
What happens when the cell cycle malfunctions?
DNA damage is carried through to subsequent cells
84
How are cancer cells grown?
Mutated tumour suppressor gene loses function And/or Mutated proto oncogene gains function
85
How may cell cycle malfunctions impact functions of a key protein?
Overactivation Inactivation
86
What does germ-line mean?
Born with
87
What is an example of germ line?
BRCA mutation
88
What does somatic mean?
Acquired
89
How often can stem cells replicate?
Indefinitely
90
How often can progenitor cells divide?
Only a limited number of times
91
What is the normal function of an oncogene?
Promotes cell growth Differentiation
92
What is the normal function of a tumour suppressor gene?
Regulates cell growth Apoptosis Genetic integrity
93
Describe the mutation of an oncogene
Dominant Only one altered copy needed
94
Describe the mutation of a tumour suppressor gene
Recessive Both copies must be altered
95
What is the effect of mutation on an oncogene?
Gain of function
96
What is the effect of mutation on a tumour suppressor gene?
Loss of function
97
What tumour suppressor gene gives a predisposition to breast/ovarian cancer?
BRCA1/2
98
What predisposition does the tumour suppressor gene P53 cause?
Li Fraumeni
99
What syndrome does tumour suppressor gene PTEN cause?
Cowden Syndrome
100
What causes adenomatous polypopsis coil?
Tumour suppressor gene APC
101
What does the tumour suppressor gene MMR cause?
Lynch Syndrome
102
What does the tumour suppressor gene Rb cause?
Retinoblastoma
103
What does the oncogene KRAS cause?
Lung/Colorectal cancer
104
What oncogene causes Lung/Colorectal/Oesophageal cancer?
EGFR
105
What does the oncogene HER2 cause?
Breast/Gastric cancer

IB Biology (4 decks)

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