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Molecular Biology And Molecular Processes > Cell Cycle > Flashcards

Cell Cycle Flashcards

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1
Q

What is mitosis ?

A

It is the process when the mitotic spindles segregate the duplicated condensed chromosomes into 2 daughter nuclei

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2
Q

What is cytokinesis ?

A

When the cytoplasm divides producing 2 genetically identical daughter cells

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3
Q

What are the 2 stages of the cell cycle ?

A

Interphase and Mitotic phase

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4
Q

What are the different processes that occur in interphase ?

A

G1
synthesis of interphase
G2

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5
Q

What is the longest part of the cell cycle ?

A

Interphase

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6
Q

What happens in Gap 1 ?

A

All organelles and the cytoplasm are replicated
The cell doubles in size

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7
Q

What happens in synthesis of interphase ?

A

The DNA is replicated

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8
Q

What happens in Gap 2 ?

A

Enzymes are created for cell division

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9
Q

What is the length of Gap 1 ?

A

~ 10 hours

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10
Q

What is the length of synthesis of interphase ?

A

~ 5-6 hours

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11
Q

What is the length of Gap 2 ?

A

~ 3-4 hours

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12
Q

What is the G0 phase ?

A

It is a temporary cell cycle state where the population of cells rest and do not replicate

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13
Q

What is another name for the G0 phase ?

A

Quiescence

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14
Q

What is terminal differentiation ?

A

It is a way of describing that cells change their phenotypic characteristics as they migrate to the surface and fully differentiate

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15
Q

How long do cells spend in mitosis ?

A

Less than one hour

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16
Q

What is generating time ?

A

The length of the cell cycle is called the generation time

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17
Q

How do cells divide ?

A

Cells have exponential growth

18
Q

What is the mitotic index ?

A

It is the percentage of time that cells spend in the mitotic phase

19
Q

How is mitotic index calculated ?

A

Cells in mitosis / total number of cells

20
Q

How is mitosis divided into stages ?

A

Mitosis is divided into stages based on the changing appearance and behaviour of chromosomes

21
Q

What are the different stages of mitosis ?

A
  • prophase : individual chromosomes become visible
  • prometaphase : fragmentation of the nuclear envelope
  • metaphase : chromosomes align at the metaphase plate
  • anaphase : sister chromatids move to opposite poles
  • telophase : nuclear envelopes and cleavage furrow forms
22
Q

Describe what happens in prophase

A
  • chromosomes condense to become compact
  • chromosomes are composed of two tightly attached chromatids
  • microtubule organising centres begin to migrate away from each other
23
Q

Describe what happens in prometaphase

A

Microtubules attach to chromosomes in the centromere region

24
Q

Describe what happens in metaphase

A
  • fully condensed chromosomes align at the metaphase plate
  • sister chromatids are actively tugged towards opposite poles
25
Q

Describe what happens in anaphase

A
  • anaphase is the shortest phase of mitosis
  • sister chromatids abruptly separate and move towards opposite poles
  • in anaphase A the chromosomes are pulled towards spindle poles
  • in anaphase B the spindle poles move away from each other as microtubules lengthen
26
Q

Describe what happens in telophase

A
  • daughter chromosomes arrive at the poles of the spindle
  • chromosomes uncoil into chromatin
  • nuclei reappear and nuclear envelopes re form
  • cytokinesis also takes place simultaneously
27
Q

Describe what happens in cytokinesis

A
  • a ring of actin and myosin forms which divides the cytoplasm into 2 cells
  • this ring is known as a contractile ring
28
Q

How does the cell cycle vary ?

A
  • the overall length of the cell cycle is variable
  • the relative length of time spent in various phases of the cell cycle is variable
  • how closely mitosis and cytokinesis are coupled is variable
29
Q

Why is the cell cycle regulated ?

A

The cell cycle is regulated to meet the needs of growth and repair per cell type and organism

30
Q

What are checkpoints ?

A

Parts of the cell cycle where stop or go signals can help or inhibit the cell from passing into the next stage of its life

31
Q

What are the different checkpoints ?

A

1) restriction point found between G1 and S phase
2) G2-M transition point found between G2 and mitosis
3) metaphase-anaphase transition point found between metaphase and anaphase

32
Q

How is the progression of cells in the cell cycle controlled ?

A
  • controlled by cyclin-dependent kinases (Cdks)
  • phosphorylation of target proteins by protein kinases activates these proteins and dephosphorylation by protein phosphatases inactivates the proteins
  • progression is only driven when the protein kinases are bound to cyclin
33
Q

What are the different types of cyclins ?

A
  • mitotic cyclins : required for G2 - M transition point
  • G1 cyclins : required for passage through the G1 restriction point
  • S cyclins : required for DNA replication
34
Q

What are the two levels of control on cyclin dependent kinase - cyclin activity?

A
  • availability of cyclin molecules
  • phosphorylation of Cdks
35
Q

Describe the process of Cdk phosphorylation

A

1) M-Cdk and M cyclin bind to form an inactive complex
2) two inhibitory phosphate groups attach to Cdk by inhibiting kinases
3) an activating phosphate group is added by activating kinase but Cdk remains inactive when an inhibitory phosphate group is present
4) phosphatase removes the inhibitory phosphate to activate the mitotic Cdk - cyclin complex

36
Q

What happens when the nuclear lamina is phosphorylated ?

A

The nuclear envelope is destabilised and breaks down

37
Q

What happens when condensin is phosphorylated ?

A

Causes chromosome condensation from euchromatin to heterochromatin

38
Q

What happens when microtubule proteins are phosphorylated ?

A

Mitotic spindles assemble

39
Q

What happens when the anaphase promoting complex is phosphorylated ?

A

Cyclin is degraded and mitosis is complete

40
Q

What is aneuploidy ?

A

When the daughter cell receives the incorrect number of chromosomes

41
Q

Describe the role of Mad & Bub proteins in relation to aneuploidy

A
  • Mad & Bub proteins accumulate at unattached kinetochores
  • they inhibit anaphase-promoting complex
  • once all chromosomes are attached Mad & Bub leave kinetochores and inhibition is lifted
  • errors cause aneuploidy

Molecular Biology And Molecular Processes (5 decks)

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