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BB10005 > Mitosis > Flashcards

Mitosis Flashcards

1
Q

Mitosis

A

shortest part of the cell cycle
Ensure accurate partitioning of the genome to daughter cells
6 phases

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2
Q

Prep for mitosis sequence

A
  1. before cell division cell has 6 chromosomes, 2 sets of 3 each
  2. Chromosome repl produces 6 pairs of sister chromatids
  3. Nucleus breaks apart and repl chromosomes condense in prep for mitois
  4. SIster chromatids separate during mitosis, and 2 cells formed during cytokinesis
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3
Q

Cyclins regulate cell cycle via

A

CDKs

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4
Q

How do cyclins regulate

A

bind to and activate CDKs enzymes

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5
Q

Cyclin-CDKs phosphorylate

A

key players in the cell cycle
Which initiate dna repl
Also phosphorylate lamins- nuclear envelope breakdown

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6
Q

how are cyclins targeted for destruction

A

ubiquitination

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7
Q

Ubiquitination

A

ubiquitin added to a protein, destruction complex targets that protein eg APC/C

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8
Q

2 phases of repl and separation

A
  1. repl all the dna, once: S phase

2. Divide copies from one nucleus into 2: mitosis

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9
Q

homologous chromosomes

A

one paternal, one maternal

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10
Q

sister chromatids

A

two copies of replicated chromosome

two maternal, two paternal (together)

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11
Q

What keeps replicated sister chromatids together

A

cohesion rings

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12
Q

How do you replicate dna only once

A

origins of repl ‘fire’ once per S phase

Cyclin -cdk complexes destroyed by APC/C

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13
Q

If you remove a protein that activates the APC/C, Emi1

A

Replication origins keep firing

Cells never enter M phase

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14
Q

When does polarisation of microtubules into bipolar spindle begin

A

In S/G2 with duplication of the centrosome (MTOC)

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15
Q

centrosome

A

centrioles and mass of proteins called pericentriolar materia

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16
Q

centriole

A

replicate in S/G2

split into 2 and travel to opposite poles at the start of mitosis

17
Q

prophase

A

chromosome condensation:

  • cohesin holds sister chromatids together
  • condensins have a similar ring structure to cohesins, further loop chromatin into tight bundles

centrosomes move apart, begin to form spindle
nucelar envelope intact

18
Q

Prometaphase

A

nuclear envelope breaks down:

  • phosphorlyation of lamins by cyclin B-CDK1
  • fragments from vesicles
  • vesicles contain lamin B, not lamin A/C
  • nuclear pore complexes (phosphorylated) diassemble

centrosome attaches to chromatids via kinetochore

19
Q

Metaphase

A

sister chromatids line up on metaphase plate
Dynamic instability- MTs grow slowly by adding subunits, shrink rapidly
Physical force from dynamic MTs orients mitotic spindle

20
Q

mitotic spindle orientation

A

sensitive to physical constraints: reorients when microtubules cut with a laser
spindle orientation important for tissue patterning/development

21
Q

What happens if tissue patterning goes wrong

A

cancer

22
Q

Parallel division of cells

A

stem cells

stay in one layer

23
Q

Perpendicular division of cells

A

differentiation

cells travel up through the layers

24
Q

kinetochore

A

protein complex linking chromatin and microtubules

CENP-B protein binds 17 bp sequence in centromeric chromatin

Sensor proteins monitor attachment to microtubules

25
Q

what does the force of microtubule dynamics do

A

pushes/pulls chromatids
Balance of forces when aligned on equator
sensor proteins also sense tension

26
Q

MCC

A

mitotic checkpoint complex
Inhibits APC when kinetochores are exposed
Exposed Kinetochores catalyse MCC formation

27
Q

When all kinetochores attached to spindle..

A

APC released and activated, targets securin for degradation, which usually inhibits separase

Separase free to cleave cohesion, initiating anaphase

28
Q

How is this a negative feedback loop

A

just one exposed kinetochore stops APC

signal amplified through kinases

29
Q

Anaphase

A

cohesin degraded

sister chromatids move to opposite poles

30
Q

Telophase

A

nuclear envelope reforms around chromosomes
Microtubules bundle and push nuclei apart
contractile ring forms on midline (will become cleavage furrow)

31
Q

cytokinesis

A

contractile ring cinches and pinches
Actin-myosin fibres slide against one another
Midbody forms at scission point, cells detach

32
Q

failure in cytokinesis

A

produces binucleate cells

BB10005 (27 decks)

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