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Cell and Molecular Biology > Mitosis, Meiosis and Cell Cycle > Flashcards

Mitosis, Meiosis and Cell Cycle Flashcards

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1
Q

Outline the different components of interphase

A

G1: cellular contents duplicated
S: DNA replication
G2: DNA repairs + checks for errors

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2
Q

Outline prophase

A
  • DNA supercoils
  • centrosomes move to opposite poles
  • spindle microtubules start to form
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3
Q

Outline metaphase

A
  • chromosomes line up at equator
  • spindle microtubules attach to centromeres of chromosomes
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4
Q

Outline prometaphase

A
  • nuclear membrane breaks down
  • chromosomes can attach to spindle microtubules via their kinetochores
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5
Q

Outline anaphase

A
  • contraction of the spindle microtubules separates the sister chromatids
  • sister chromatids are pulled towards the opposite poles of the cell
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6
Q

Outline telophase

A
  • The two sets of chromosomes arrive at the poles
    -A new nuclear envelope reassembles
  • the formation of 2 nuclei and marking the end of mitosis
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7
Q

Outline animal cytokinesis

A

cleavage furrow is formed

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8
Q

Outline plant cytokinesis

A

cell plate joins the plasma membrane

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9
Q

What is the function of condensin

A

it ensures the proper segregation of chromosomes into daughter cells by compacting DNA strands

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10
Q

What is the function of cohesion

A

it holds the sister chromatids together after DNA replication

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11
Q

Why is the cohesion complex important in the cell cycle

A
  • ensures chromatids are properly aligned and attached to microtubules
  • w/o sister chromatids separate badly leading to errors
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12
Q

What is meant by SMC complexes

A
  • cohesin + condensin complex
  • structural maintenance of chromosomes
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13
Q

What is the role of SMC complexes

A

maintain structure of chromosomes

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14
Q

What causes the breakdown and formation of the nuclear envelope

A
  • mitotic CDK are inactive = formation of nuclear envelope (phosphorylation)
  • mitotic CDK are active due to dephosphorylation = breakdown of nuclear envelope
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15
Q

What are the 3 types of microtubules

A
  • Aster microtubules
  • Kinetochore microtubules
  • Interpolar microtubules
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16
Q

What is the role of kinetochores

A

-it enables the attachment of spindle microtubules on chromosomes

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17
Q

How microtubules separate sister chromatids in anaphase A

A

chromosomes are pulled poleward
(shortening of microtubules)

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18
Q

How microtubules separate sister chromatids in anaphase B

A

the poles are pulled (spindle poles move apart)

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19
Q

What is the function of APC

A

it promotes the destruction of cyclins to allow mitosis to end

20
Q

What happens when mitotic cyclins are destroyed

A

End of mitosis and restart of interphase (G1 phase)

21
Q

What causes genetic variation in meiosis

A
  • crossing over
  • random orientation
22
Q

What is crossing over

A

the exchange of DNA between non-sister chromatids at the chiasma

23
Q

What is random orientation

A

homologous chromosomes line up in metaphase I their orientation towards the poles is random

24
Q

What is non-disjunction

A

an error in meiosis, where the chromosome pairs fail to split correctly during cell division

25
Q

When does non-disjunction occur

A

Anaphase I or Anaphase II

26
Q

What is an example of non-disjunction

A

Down syndrome (3 chromosomes on 21)

27
Q

What are some differences between mitosis and meiosis

A

mitosis: somatic cell, diploid, 2 daughter cells, cancer
meiosis: gametes, haploid, 4 daughter cells, genetic mutations

28
Q

What is mutagenesis

A

the production of genetic mutations

29
Q

How to identify genes that are involved in the cell cylce via mutagenesis

A
  1. Cause mutations in cells
  2. isolate the temp.-sensitive mutants
  3. researchers can identify genes essential for a proper cell cycle
  4. if mutant genes are involved in cell cycle, abnormal cell division would occur
30
Q

What is the purpose of checkpoints during the cell cycle

A

prevent mistakes from happening and to avoid abnormal cell division

31
Q

Where are the 3 main cell cycle checkpoints located at

A

G1, G2 and M

32
Q

What does the checkpoint at G1 do

A

it determines if all the conditions are good for the cell to divide
- this is when the cell irreversibly commits to cell division

33
Q

What does the checkpoint at G2 do

A

it ensures that all the DNA has been replicated and there is no damaged DNA

34
Q

What does the checkpoint at M do

A

it determines if all the chromosomes are arranged correctly for segregation
- if not checked = non-disjunction

35
Q

What are cyclins

A

regulatory proteins that control the progression of the cell cycle

36
Q

How do cyclins control the cell cycle

A
  1. Cyclin + CDK = cyclin-CDK complex
  2. cyclin-CDK complex is phosphorylated –> activated
  3. activated cyclin-CDK phosphorylates target protein
  4. activated protein advances in cell cycle
37
Q

what is the main function of CDC2

A

a CDK that controls the transition from G2 to M

38
Q

Outline how CDC2 is activated

A
  1. During G2, CDC2 is inactivated by WEE1
  2. When the cell is ready to enter mitosis, CDC25 dephosphorylates CDC2 –> active
  3. now active CDC2 drives cell into mitosis
39
Q

Outline how CDC2 is inhibited

A
  1. When DNA replication is not complete or DNA is damaged, CDC2 needs to be inactive
  2. WEE1 phosphorylates CDC2
  3. this stops cell entry into mitosis
40
Q

What is the role of MPF

A

it phosphorylates target proteins triggering the start of mitosis (cyclin B, G2 to M)

41
Q

What is the role of APC

A

it promotes cyclin destruction and mitotic exit

42
Q

3 Main consequences of MPF

A
  • chromosomes condense
  • nuclear membrane breakdown
  • spindle microtubule forming
43
Q

How does APC promote cyclin destruction and mitotic exit

A
  1. APC targets cyclin B for destruction (responsible for driving cell into mitosis)
  2. destruction of cyclin B leads to inactivation of MPF
  3. the degradation of cyclin allows for chromosomes to decondense + formation of 2 daughter cells + nuclear membrane reforms
44
Q

What triggers telophase to start

A

the destruction of cyclins

45
Q

What occurs if the DNA breaks

A

cell death or DNA repair

46
Q

What occurs if there is an accumulation of broken chromosomes

A

genome instability and can lead to cancer (uncontrolled cell growth)

47
Q
A

Cell and Molecular Biology (8 decks)

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