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From Molecules to Cells > Lecture 12: Prophase and prometaphase > Flashcards

Lecture 12: Prophase and prometaphase Flashcards

1
Q

What are cyclin dependent kinases (cdk) ?

A

Drive cell cycle
Phosphorylate key proteins to control function in cell cycle

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2
Q

What are the key things that must occur before mitosis?

A

Cell increases in size
DNA replicated
Centrosome duplicated
Organelles grow
Cohensin rings are added to hold sister chromatids together until anaphase

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3
Q

How does centrosome duplication occur?

A

Triggered by Cdk to duplicate in S phase

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4
Q

What is the role of centrosomes in mitosis?

A

Migrate to two spindle poles
Nucleate microtubules

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5
Q

What are the three different groups of microtubules in the mitotic spindle?

A

Kinetochore microtubules
Interpolar microtubules
Astral microtubules

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6
Q

What are kinetochore microtubules?

A

Microtubules that find and attach to the kinetochores
Undergo coordinated assembly and disassembly

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7
Q

What are interpolar microtubules?

A

Grow from one polar and meet those from the other pole
Form antiparallel interactions

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8
Q

What are astral microtubules?

A

Dynamic with a crucial role in anaphase

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9
Q

How is the mitotic spindle set up?

A

Number of microtubules nucleated by centrosomes increases
Microtubules are more dynamic
Catastrophe occurs where microtubules shrink more often

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10
Q

Why do dynamics of the microtubules increase in setting up the microtubules?

A
  1. Some microtubule associated proteins are inactivated when phosphorylated by M-Cdk
  2. Proteins that trigger catastrophe are activated
  3. More chance of microtubules growing from each centrosome contacting each other or chromosomes
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11
Q

What occurs when condensin is activated via phosphorylation by M-Cdk?

A

Chromosomes condense

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12
Q

What occurs when microtubule catastrophe proteins are activated via phosphorylation by M-Cdk?

A

Microtubules get more dynamic

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13
Q

What happens when microtubule associated proteins are inactivated via phosphorylation by M-Cdk?

A

Microtubules are more dynamic

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14
Q

What happens when nuclear lamins are inactivated via phosphorylation by M-Cdk?

A

Nuclear envelope disassembles

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15
Q

What happens to the chromosomes in prophase?

A

Condense due to condensin activation

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16
Q

What happens to the mitotic spindle in prophase?

A

Starts forming
Microtubules from the centrosomes meet and have antiparallel interaction
Overlap zone between microtubules drives pole separation

17
Q

How does the overlap zone between microtubules drive pole separation?

A

Kinesin Eg5 cross links antiparallel microtubules and pushes the centrosome apart to form the spindle poles

18
Q

What is the role of Eg5 and bipolar spindle formation?

A
  1. Antiparallel interactions mediated by Eg5 stabilise microtubules
  2. Eg5 inhibition stops the centrosomes from separating
  3. Leads to a monopolar spindle
  4. This means the presence of Eg5 causes the bipolar spindle
19
Q

What happens to the nuclear envelope in prometaphase?

A

Disassembles

20
Q

How does the nuclear envelope disassemble during prometaphase in animal cells?

A

Nuclear lamina disassembles

21
Q

How does the nuclear envelope disassemble during prometaphase in plant cells?

A

No nuclear lamins but envelope still disassembles

22
Q

What happens to the golgi apparatus in prometaphase?

A

Fragments so each cell gets an equal amount
Secretion and endocytosis stop

23
Q

What is the kinetochore?

A

Protein structure that assembles on centromere during prophase
Attaches chromosomes to microtubules and moves along them using microtubule motors

24
Q

In what direction does the kinetochore move along microtubules?

A

Both directions

25
Q

How do the microtubules move at the kinetochore?

A

Grow and shrink together in a coordinated way
Assembly and disassembly drives chromosome movement

26
Q

What are some properties of the kinetochore?

A

Specialised chromosomal structure for spindle attachment
Binds multiple MTs at once
Move in both directions by harnessing assembly and disassembly using MT motors
Under tension whilst attached to both poles which is needed for mitosis

From Molecules to Cells (23 decks)

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