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EOM 1 - Test 3 > Brazeau - Mitosis > Flashcards

Brazeau - Mitosis Flashcards

1
Q

Prophase

A

Chromosomes condense, initial formation of spindles, nuclear envelope breaks down

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2
Q

Metaphase

A

Spindle microtubules attach to kinetochore, chromosomes align at center of spindles

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3
Q

Anaphase

A

Sister chromatids separate and move to poles

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4
Q

Telophase

A

Reformation of nucelar envelope, chromosome decondensation

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5
Q

Checkpoint that must be passed to enter mitosis?

A

G2 Checkpoint

  • DNA Completely synthesized
  • No DNA Damage

CDK1/Cyc B

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6
Q

What regulates transition from G2 to M phase?

A

MPF

CDK1 and Cyclin B

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7
Q

What is the role of MPF?

A

Once activated, phosphorylates downstream targets responsible for mitosis in positive feedback loop with Aurora Kinase/Polo-like Kinase

  1. Chromatin Condensation
  2. Nuclear Envelope Breakdown
  3. Fragmentation of Golgi
  4. Spindle formation
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8
Q

What is popular target for cancer drugs in the cell cycle?

A

Spindle formation in prophase

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9
Q

During DNA replication (S phase), what binds sister chromatids along full length?

(e.g. what maintains linkage of newly synthesized sister chromatids)

A

Cohesins

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10
Q

What does condensin require to promote condensation of chromatin?

A

ATP

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11
Q

What drives the shift from cohesin to condensin?

A

Cyc B, CDK 1, PLKinas

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12
Q

In what phases do each chromosome consist of two sister chromatids until separation at anaphase?

A

G2 and M

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13
Q

During G2 what holds sister chromatids together along their length?

What occurs during prophase?

A

Cohesin

Cohesin is removed from most of the length–but stays at the centromere; at the same time condensin begins to condense chromosomes

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14
Q

When are the chromosomes completely condensed?

A

Metaphase

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15
Q

What initiates nuclear envelope breakdown?

A

Lamins depolymerize when phosphorylated by MPF (CycB/CDK1)

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16
Q

What works in tandem to push spindle poles apart?

A

Polar (Inter) and Astral Microtubules

17
Q

What regulates assembly and disassembly of microtubules?

18
Q

What is the role of the microtubules in chromosome separation?

A

Ensure alignment and movement of chromosomes

19
Q

Taxol

A

Cancer drug which stabilizes microtubules and interferes w/ability to align the chromosome

20
Q

What special proteins are located at the centromere? What is their purpose?

A

Histone H3-like Centromeric Protein (CENP)

Bind DNA and kinetochore proteins for attachment of mitotic spindle

21
Q

What is the protein complex that bind centromere and spindle microtubules?

A

Kinetochore

22
Q

What is the equidistant alignment point from both spindles?

A

Metaphase Plate

23
Q

What phase is the Spindle Checkpoint?

24
Q

Mitotic Checkpoint Complex (MCC)

What important protein is part of the complex–and what is its role?

A

Formed at unattached kinetochores and inhibits APC

Cdc20 – required activator of APC

25
Q

Once microtubules attach to kinetochore, what happens?

A

MCC no longer formed; Cdc20 is freed

Free to activate APC (degrade CycB)–trigger anaphase

26
Q

What event triggers the exit from mitosis?

A

Degradation of Cyclin B

27
Q

What is the role of APC?

A

Ubiquitin Ligase (E3 Enzyme) that makes proteins for degradation by proteosomes.

28
Q

What are the main targets of APC?

A

Securin and Cyclin B

Cyclin B destruction inactivates Cdk1

Securin destruction activates Sepase; freeing Cohesin from centromere

29
Q

What must be completed before Cyclin B is degraded?

What happens when this is not completed?

A

Chromosome segregation

Nondisjunction; results in aneuploidy

30
Q

What is the push and pull of chromosome separation?

A

Push = Polar microtubules via plus end directed motor proteins

Pull = Astra microtubules move spindle toward cell periphery via minus end directed motor proteins

31
Q

When do Cyclin B levels peak?

What declines with Cyclin B degradation?

What does a decrease in MPF activity permit?

A

Cyclin B peaks during mitosis

MPF activity, Aurora/PLKinase declin with CycB degradation

Decrease in MPF permits telophase and cytokinesis to proceed

32
Q

What promotes reassembly of nuclear membrane?

A

Low kinase activity

Dephosphorylation by Cdc14 Phosphatase

33
Q

Cleavage Furrow

A

Perpendicular to long axis of cell, midway between poles

Emits signal for formation of contractile ring

34
Q

What two proteins pinch off the contractile ring?

A

Myosin2

Actin

35
Q

What prevents activation of myosin 2 before anaphase?

What creates environment for activation of myosin II?

What triggers contraction of ring and cytokinesis?

A

High MPF activity

MPF activity decrease due to APC

Transient increae in intracellular calcium activates MLC kinase

36
Q

What are the major 2 checkpoints of mitosis?

A

G2 - complete DNA replication, no DNA damage

Spindle Assembly - All chromosomes have bipolar attachment

37
Q

What activates APC?

What degrades CycB/CDK1?

EOM 1 - Test 3 (18 decks)

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