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MBB 231 > Lecture 19 - Mitosis & Cytokinesis > Flashcards

Lecture 19 - Mitosis & Cytokinesis Flashcards

1
Q

def: phase where duplication of all DNA in a cells chromosomes occur

A

S-Phase

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2
Q

def: phase where copies of chromosomes are segregated into the two daughter cells

A

M-phase

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3
Q

the Gap phases (G1/G2) allow time for cells to:

A
  • double their mass of proteins and organelles
  • monitor the fidelity of other processes
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4
Q

T or F: cells spend very little time in M-phase

A

true

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5
Q

where is most of the time spent in the cell cycle?

A

interphase (G1, S, and G2)

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6
Q

def: when the cells actually divide, the nucleus first, followed by the cytoplasm

A

M phase

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7
Q

why is chromosome condensation critical?

A

interphase chromatin fibres are too long and intertwined, would be impossible to untangle and distribute during cell division

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8
Q

how does the entire microtubule cytoskeleton disassemble as the cells progress from G2 into M phase?

A
  • inactivation of stabilizing MAPs (Tau, MAP2, EB1)
  • activation of destabilizing MAPS (Stathmin, Catastrophins, Katanins)
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9
Q

when does centriole duplication occur?

A

S phase

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10
Q

when do the centrioles separate?

A

during prophase to act as nucleation sites to form the mitotic spindle

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11
Q

dissolution of the nuclear envelope marks the onset of ___________________

A

prometaphase

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12
Q

the dissolution of the nuclear envelope allows what to occur?

A

allows the spindle microtubules to make contacts with the chromosomes

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13
Q

phosphorylation of ______________ proteins induces chromatin condensation and inhibits interactions between chromatin and the nuclear envelope

A

chromatin

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14
Q

phosphorylation of specific ________________ causes nuclear pore complexes to dissociate

A

nucleoporins

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15
Q

phosphorylation of _____________________ inhibits their interaction with lamina and with chromatin

A

inner nuclear membrane proteins

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16
Q

phosphorylation of human ________ _ causes depolymerization of the intermediate filament in the Nuclear Lamina

A

Lamin A

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17
Q

the mitotic spindle is completed when…..

A

the (+) end of MT’s from each spindle pole bind the sister chromatid at the kinetochores

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18
Q

def: process the begins as chromosomes move to the center

A

congression

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19
Q

microtubules attach to chromosomes in the ___________ region, at structures called _______________

A

centromeric, kinetochores

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20
Q

DNA in centromeres consists of simple, tandemly repeated _____ ________________, with considerable variation among species

A

CEN sequences

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21
Q

what is a common feature among species within the centromere?

A

presence of a histone H3-related protein called CENP-A (humans_

22
Q

def: recruits additional proteins to the centromere to form the kinetochore to which MT’s attach

A

CENP-A

23
Q

def: bi-directional forces exerted by kinetochore bound microtubules from each bole gradually move chromosomes toward the centre of the cell

A

congression

24
Q

def: responsible for chromosome movements and separation of chromatids during mitosis

A

mitotic spindle

25
Q

where are the centrosome and kinetochore located on a microtubule

A
  • the centrosome contains the (-) end
  • the kinetochore attaches to the (+) end
26
Q

kinetochores are the site of :

A
  1. microtubule/chromosome attachment
  2. motor proteins, necessary for chromosome mobility
  3. signalling for important mitotic checkpoints
27
Q

when is a cell considered to be in metaphase?

A

when the fully condensed chromosomes are aligned at the metaphase plate

28
Q

T or F: the mitotic spindle is a stable structure

A

False, it is highly dynamic, it treadmills

29
Q

the kinetochore should not be viewed as a cap protein, there is a ______ ______ of tubulin at the ____________ and a ________ at the kinetochore

A

net loss at centriole, net gain at the kinetochore

30
Q

def: project toward the cell cortex, help position the spindle apparatus in the cell

A

astral microtubule

31
Q

def: connect to chromosomes to the spindle poles, alight the chromosomes on the metaphase phase and pull them to the poles during anaphase

A

kinetochore microtubules

32
Q

def: extend past the chromosomes and interact with polar microtubules from the other spindle pole, maintain integrity of the mitotic spindle and push the spindle poles apart during anaphase

A

polar microtubules

33
Q

what is the shortest phase of mitosis

A

anaphase

34
Q

def: abruptly separates connections between the two sister chromatids of each chromosome, allowing for movement toward the opposite poles

A

Separase

35
Q

def: portion of anaphase where chromosomes slowly pulled centromere first toward spindle poles as kinetochore microtubules get shorter

A

anaphase A

36
Q

def: portion of anaphase where the spindle poles themselves move away from each other as polar microtubules lengthen

A

anaphase B

37
Q

def: bind to the ends and promotes depolymerization of MT’s at both the kinetochores an centrosome

A

specialized kinesisn

38
Q

def: bind to overlapping polar microtubules, cause them to move apart

A

bi-polar kinesin 5

39
Q

def: when associated with astral microtubules, moves towards the (-) ends of microtubules, pulling the spindle poles toward the cell membrane

A

cytoplasmic dynein

40
Q

where does the force required to move chromosomes toward the mitotic poles come from?

A

depolymerization of the kinetochore MT

41
Q

the depolymerizing kinesis removes tubulin from the :

A

(+) end = pulling the chromosome towards the pole as the MT disassemble
(-) end = enhancing poleward microtubule flux

42
Q

def: connect MT’s to kinetochores, move along MT maintaining contact as depolymerization occurs

A

6-9 Ndc80 complexes

43
Q

what 4 things happen during telophase?

A
  1. daughter chromosomes arrive at the poles of the spindle
  2. mitotic spindle disassembles
  3. chromosomes uncoil into interphase chromatin
  4. nucleoli reappear and nuclear envelopes reform
44
Q

signals emanating from the central part of the spindle, the spindle mid zone, are important for establishing where __________ will occur

A

furrowing

45
Q

cleavage depends on a belt-like bundle of _________ ____________ that form just below the plasma membrane in early anaphase

A

actin microfilaments

46
Q

what is contraction of the contractile ring generated by?

A

interactions between actin and bipolar myosin II motor proteins

47
Q

what regulates the assembly and activation of the contractile ring?

A

members of Rho family

48
Q

def: final separation of daughter cells

A

abscission

49
Q

how are large, multi-nucleated cells produced?

A

when a cell undergoes incomplete cell division, mitosis but no cytokinesis

50
Q

control of the cell cycle must:

A
  1. ensure events of each phase are carried out in the correct order and at the appropriate time
  2. ensure that each phase is completed before the next one begins
  3. respond to external conditions
51
Q

what are the 3 major checkpoints in eukaryotic cells?

A
  1. start (or restriction point) - cell commits to cell-cycle entry
  2. G2/M checkpoint
  3. metaphase to anaphase checkpoint - chromatid separation is triggered leading to completion of mitosis and cytokinesis

MBB 231 (19 decks)

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