Lecture 19 - Mitosis & Cytokinesis

Question 1

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

Answer 1

S-Phase

Question 2

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

Answer 2

M-phase

Question 3

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

Answer 3

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

Question 4

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

Answer 4

true

Question 5

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

Answer 5

interphase (G1, S, and G2)

Question 6

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

Answer 6

M phase

Question 7

why is chromosome condensation critical?

Answer 7

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

Question 8

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

Answer 8

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

Question 9

when does centriole duplication occur?

Answer 9

S phase

Question 10

when do the centrioles separate?

Answer 10

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

Question 11

dissolution of the nuclear envelope marks the onset of ___________________

Answer 11

prometaphase

Question 12

the dissolution of the nuclear envelope allows what to occur?

Answer 12

allows the spindle microtubules to make contacts with the chromosomes

Question 13

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

Answer 13

chromatin

Question 14

phosphorylation of specific ________________ causes nuclear pore complexes to dissociate

Answer 14

nucleoporins

Question 15

phosphorylation of _____________________ inhibits their interaction with lamina and with chromatin

Answer 15

inner nuclear membrane proteins

Question 16

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

Answer 16

Lamin A

Question 17

the mitotic spindle is completed when…..

Answer 17

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

Question 18

def: process the begins as chromosomes move to the center

Answer 18

congression

Question 19

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

Answer 19

centromeric, kinetochores

Question 20

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

Answer 20

CEN sequences

Question 21

what is a common feature among species within the centromere?

Answer 21

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

Question 22

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

Answer 22

CENP-A

Question 23

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

Answer 23

congression

Question 24

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

Answer 24

mitotic spindle

Question 25

where are the centrosome and kinetochore located on a microtubule

Answer 25

- the centrosome contains the (-) end - the kinetochore attaches to the (+) end

Question 26

kinetochores are the site of :

Answer 26

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

Question 27

when is a cell considered to be in metaphase?

Answer 27

when the fully condensed chromosomes are aligned at the metaphase plate

Question 28

T or F: the mitotic spindle is a stable structure

Answer 28

False, it is highly dynamic, it treadmills

Question 29

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

Answer 29

net loss at centriole, net gain at the kinetochore

Question 30

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

Answer 30

astral microtubule

Question 31

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

Answer 31

kinetochore microtubules

Question 32

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

Answer 32

polar microtubules

Question 33

what is the shortest phase of mitosis

Answer 33

anaphase

Question 34

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

Answer 34

Separase

Question 35

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

Answer 35

anaphase A

Question 36

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

Answer 36

anaphase B

Question 37

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

Answer 37

specialized kinesisn

Question 38

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

Answer 38

bi-polar kinesin 5

Question 39

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

Answer 39

cytoplasmic dynein

Question 40

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

Answer 40

depolymerization of the kinetochore MT

Question 41

the depolymerizing kinesis removes tubulin from the :

Answer 41

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

Question 42

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

Answer 42

6-9 Ndc80 complexes

Question 43

what 4 things happen during telophase?

Answer 43

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

Question 44

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

Answer 44

furrowing

Question 45

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

Answer 45

actin microfilaments

Question 46

what is contraction of the contractile ring generated by?

Answer 46

interactions between actin and bipolar myosin II motor proteins

Question 47

what regulates the assembly and activation of the contractile ring?

Answer 47

members of Rho family

Question 48

def: final separation of daughter cells

Answer 48

abscission

Question 49

how are large, multi-nucleated cells produced?

Answer 49

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

Question 50

control of the cell cycle must:

Answer 50

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

Question 51

what are the 3 major checkpoints in eukaryotic cells?

Answer 51

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