lecture 11

Question 1

what needs to happen for cell division

Answer 1

microtubules rearrange, form mitotic spindle machine, evenly split genetic info

Question 2

step 1 of cell cycle

Answer 2

grows; needs more of everything, including DNA/chromosomes, b/c it’s splitting

Question 3

step 2 of cell cycle

Answer 3

after growth/synthesis phase, cell undergoes split of chromosomes into daughter cells (chromosome segregation)

Question 4

step 3 of cell cycle

Answer 4

actual cell division; split into 2/cytokinesis

Question 5

S phase

Answer 5

synthesis; cells need to grow and duplicate DNA

Question 6

M phase

Answer 6

mitosis; split chromosomes evenly among daughter cells, includes cytokinesis

Question 7

interphase

Answer 7

cell doesn’t seem to do anything, but it’s actually undergoing S phase

Question 8

M phase

Answer 8

prophase, prometaphase, metaphase, anaphase, telophase

Question 9

phases in interphase

Answer 9

G1, S, G2

Question 10

what controls transitions b/w phases

Answer 10

checkpoints; is everything okay? ex. are all chromosomes attached to mitotic spindle (metaphase to anaphase)

Question 11

what controls timing b/w phases of cell cycle

Answer 11

these checkpoints

Question 12

reg. protein complex that controls when cells go from one phase to another

Answer 12

cyclin-dependent kinase complex

Question 13

what specifically controls diff transitions of cell cycle

Answer 13

kinase activity

Question 14

what happens when checkpoints are satisfied

Answer 14

signals activate CDK, phosphorylate downstream targets to initiate next phase

Question 15

what needs to be bound to complex for it to be active

Answer 15

cyclin

Question 16

what happens if no cyclin

Answer 16

kinase is inactive

Question 17

what controls CDK activity to allow transition from one phase to another

Answer 17

expression of cyclin

Question 18

what happens as you go thru cell cycle

Answer 18

cyclin expression goes up and down

Question 19

describe CDK expression

Answer 19

constant

Question 20

when is CDK active

Answer 20

when cyclin is bound

Question 21

describe CDK thru cell cycle

Answer 21

expression doesn’t change, but activity changes based on cyclin [ ]

Question 22

what is cyclin for M-CDK

Answer 22

cyclin B or cyclin M

Question 23

what does cyclin B/M do

Answer 23

controls M-CDK activity

Question 24

what is checkpoint for metaphase to anaphase pathway

Answer 24

are chromosomes successfully attached to mitotic spindle

Question 25

what happens if not attached

Answer 25

protein complex inhibited, chromosomes CANNOT segregate

Question 26

what happens if not inhibited

Answer 26

M-CDK activity is controlled, cells progress further into cell cycle

Question 27

what needs to happen to cyclin to go from metaphase to anaphase

Answer 27

M-cyclin needs to be degraded, turn off M-CDK activity

Question 28

describe mechanism for degradation of M-cyclin

Answer 28

chromosomes attached to spindle --> activates cdc20 --> binds to APC --> APC/cdc20 complex --> ubiquitilates M-cyclin and adds polyubiquitin chain, targets it for degradation by proteasome

Question 29

prophase

Answer 29

2 centrosomes (have duplicated), DNA condensed into chromosomes, nuclear envelope intact (chromosomes r in it)

Question 30

prometaphase

Answer 30

breakdown of nuclear envelope, chromosomes free to swirl around, centrosomes at opposite ends of cells, kinetochore

Question 31

metaphase

Answer 31

chromosomes attached to mitotic spindle at center

Question 32

anaphase

Answer 32

chromosomes separating, moved to opposite poles of cell

Question 33

telophase

Answer 33

right before cytokinesis; 2 centrioles in opposite poles, 2 nuclear envelopes reform

Question 34

cytokinesis

Answer 34

nuclear envelope fully formed, chromosomes decondense, actively being split

Question 35

what happens to trigger anaphase

Answer 35

as long as chromosomes attached (even if 3 instead of 2)

Question 36

mitotic spindle

Answer 36

built out of microtubules; radiate out of centrosome

Question 37

3 types of MTs

Answer 37

kinetochore microtubules, non-kinetochore microtubules, astral microtubules

Question 38

kinetochore microtubules

Answer 38

extend toward midpoint of cells (From ends), chromosomes attach here to satifsy metaphase to anaphase checkpoint

Question 39

non-kinetochore

Answer 39

extend toward midpoint, but smaller chunks; help position mitotic spindle

Question 40

astral microtubules

Answer 40

radiate away from midpoint; other drxn, at ends; help hold mitotic spindle in orientation

Question 41

individual motor proteins

Answer 41

kinesins 4&10, kinesin 5, dynein

Question 42

kinesins 4/10

Answer 42

walk chromosomes to midpoint, plus ends of kinetochore microtubules (get chromosomes to right spot)

Question 43

kinesin 5

Answer 43

4 motor domains, walks along 2 MTs; pushes apart poles by walking to plus ends (both are in opposite drxns)

Question 44

inhibit kinesin 5?

Answer 44

poles would come closer together

Question 45

kinesin 14

Answer 45

one set of motor domains, other binds to MT and carriers it as cargo; walks to minus end --> pulls poles closer together

Question 46

dynein

Answer 46

one part binds plasma membrane, walks toward minus end; pulls centrosome to plasma membrane to keep it anchored (astral MTs)

Question 47

what balances forces

Answer 47

dynein, kinesin 5, 14

Question 48

when is the idea of balancing dynamic forces needed

Answer 48

metaphase to anaphase transition; not needed after cuz mitotic spindle not needed

Question 49

how are chromosomes attached to kinetochores

Answer 49

plus ends bind perpendicular

Question 50

what is only stable kinetochore conformation

Answer 50

one side bound to one chromosome, other side bound to other chromosome

Question 51

cdc20 separase pathway

Answer 51

apc/cdc20 complex, ubiquitinates securin & destroys it, activates separase( Protease) that targets cohesins, degrades it, separating daughter chromosomes

Question 52

what happens when chromosomes are not attachedq

Answer 52

MAD20 is active

Question 53

what does MAD20 do

Answer 53

inhibits cdc20