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Cell Molec > Lecture 21 > Flashcards

Lecture 21 Flashcards

1
Q

What phase do mitotic cyclins begin to increase?

A

S-phase

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2
Q

When do mitotic CDKs increase in concentration?

A

almost at the end of G2

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3
Q

How are mitotic CDKs bound with mitotic cyclin held inactive?

A

Tyr and Thr residues are phosphorylated on CDK-inhibitor site

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4
Q

What activates the mitotic cyclin-CDK complex?

A

Cdc25 phosphatase

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5
Q

Function of mitotic CDKs

A

ensures that the spindle formation and attachment of chromosome is correct

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6
Q

What is amphitelic MT attachment

A

stable attachment with use of mitotic CDKs

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7
Q

what is merotelic MT attachment

A

one MT on one side and three on the other side

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8
Q

what makes merotelic MT attachment unstable?

A

aurora B phosphorylates with each other = loose unstable attachment

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9
Q

what is syntelic MT attachment

A

MTs from only one side attach to both sides of kinetchores

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10
Q

what is monotelic MT attachment

A

MTs only attach to one side of kinetochores

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11
Q

In the cell cycle, when do we want to remove the centromere cohesins?

A

before anaphase happens

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12
Q

What checkpoint in the cell cycle checks for amphitelic MT attachment and correct orientation of MT spindles??

A

spindle checkpoint

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13
Q

What is securin?

A

a protein that inactivates separase

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14
Q

What is the function of separase?

A

cleaves off cohesins of chromosomes

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15
Q

How is separase activated?

A

APC/C ubiquitinylates securin for degradation = activates separase

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16
Q

What is Cdc14?

A

a protein phosphatase

17
Q

What is beneficial about Cdc14 with Sic1?

A

it keeps Sic1 unphosphorylated to prevent DNA replication from happening before S-phase

18
Q

When is APC/C the most active?

A

right after mitosis

19
Q

What phosphorylates Cdh1 of APC/C to inactivate it? Why?

A

G1/S-phase CDKs to prevent degradation of G1/S-phase cyclins and CDKs

20
Q

What is Sic1 attached to and what needs to be done in order to move onto DNA replication?

A

phosphorylate Sic1 which is attached to the S-phase cyclins/CDKs and inactivates it

21
Q

What holds the mitotic cyclin/CDK complex inactive prior to mitosis?

A

Wee1 kinase

22
Q

What phosphorylates Cdh1 to activate APC/C?

A

Cdc14

23
Q

If the cell’s surveillance mechanisms (cell cycle checkpoints) detect DNA damage, what happens?

A

pauses cell cycle and allows DNA to repair while preventing the start of mitosis

24
Q

What are the three options that a cell can take once DNA damage has been detected and the phosphorylated kinases are ready to fix the problem?

A

DNA repair, prevent Cdc25 functions, or activate p53

25
Q

Which cycle does the cell initially check for DNA damage? What, then, happens?

A

G1, p21 prevents the expression of G1 CDKs = pauses cell cycle

26
Q

If DNA damage is detected in S-phase, what happens?

A

cell cycle prevents G1/S-phase CDKs from activating DNA synthesis

27
Q

If replication stress is detected in S-phase, what happens?

A

S-phase CDKs are inactivated = pauses cell cycle

28
Q

If DNA replication happened late, what happens?

A

cell cycle is stopped to ensure that DNA replication is completely done prior to mitosis

29
Q

what does the spindle assembly checkpoint checks for?

A

correct chromosome attachment to spindles prior to segregation, chromosomes must be under tension

30
Q

What happens if the kinetochore complex are not attached to MT?

A

kinetochore complex will be phosphorylated = leads Mitotic Checkpoint Complex (MCC) to associate with APC/C to inactivate it = pause cell cycle to allow MT attachment

31
Q

What does the Spindle Position Checkpoint pathway check for?

A

nucleus is accurately partitioned between two daughter cells, spindles must be positioned correctly

32
Q

What is different about meiosis compared to mitosis?

A

only happens in gametes, homologous chromosomes, daughter cells are not genetically identical, reduction division and crossing over happens

33
Q

What is meiosis I also called?

A

reduction division (cells still 2n)

34
Q

What is meiosis II equivalent to?

A

mitosis when 2n –> n

35
Q

What is Rec8?

A

cohesin used in meiosis between sister chromatids

36
Q

When does Rec8 get cleaved off?

A

Metaphase II

Cell Molec (16 decks)

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