3.7 first half

Question 1

what are the phases of the cell cycle?

Answer 1

• G1 phase (cells just hanging out)
  -G0 (cellular state outside of the replicative cell cycle)
  -S phase: replicate
  -G2: get ready to divide
  -M: mitosis –> cytokinesis

Question 2

steps of mitosis

Answer 2

1. prophase
2. prometaphase
3. metaphase
4. anaphase
5. telophase

Question 3

what happens in prophase?

Answer 3

• replicated chromosomes condense
• mitotic spindle assembles between 2 chromosomes

Question 4

what happens in prometaphase?

Answer 4

-breakdown of nuclear envelope
- chromosomes attach to spindle microtubules

Question 5

what happens in metaphase?

Answer 5

-chromosomes aligned at equator of spindle

Question 6

what happens in anaphase?

Answer 6

paired chromatids separate to form 2 daughter chromosomes

Question 7

what happens in telophase?

Answer 7

• daughter chromosomes arrive at poles of spindle
• formation of 2 nuclei
• assembly of contractile ring

Question 8

what happens in cytokinesis?

Answer 8

cytoplasm is divided in two

Question 9

what are the 3 types of cytoskeletal filaments?

Answer 9

1. intermediate
2. microtubules
3. actin

Question 10

________ filaments give the cell a semi-permanent shape against mechanical stress

Answer 10

intermediate

Question 11

________ provide a track for intracellular transport, and are easily disassembled/assembled to fit transport needs of the cell

Answer 11

microtubules

Question 12

_________ function in membrane mobility, cell movement, and temporary cell structure for when cell changes its shape

Answer 12

actin filaments

Question 13

what is intermediate filament structure like?

Answer 13

8 tetramers twisted into a rope-like filament

Question 14

_________ are filaments that support the nuclear envelope and must be broken down for the nuclear envelope to breakdown

Answer 14

Lamin IFs

Question 15

how does the nuclear envelope breakdown and buildback up with the help of Lamins?

Answer 15

1. lamins get phosphorylated
2. filaments breakdown and take a little piece of the membrane with them
3. they go and get pushed off to the side
4. in telophase they get brought back and stick to/surround chromatids
5. lamins de-phosphorylated
6. pieces of envelope fuse back together

Question 16

MTs form the _____ in prophase

Answer 16

mitotic spindle

Question 17

MT are unidirectional and can only grow in the _____ direction

Answer 17

negative to positive

Question 18

a temporary MT railroad is set up to do what?

Answer 18

so motor proteins can move cell bits to either side

Question 19

how many types of tubulins are MT made of?

Answer 19

3 (all types of alpha/beta)

Question 20

how do MT grow?

Answer 20

-dimers are kinked at first
-nucleotide exchange from GDP –> GTP
- when dimer has GTP it is no longer kinked and can be added to the growing polymerization
- GTP is removed, but since the dimers are stuck in the tubule they cant kink

Question 21

what is the amount of kinking in the MT controlled by?

Answer 21

how quickly GTPase activity happens (less strained = easier to add subunits)

Question 22

if the GTP < GDP what happens?

Answer 22

MT will unravel

Question 23

If GTP>GDP what will happen?

Answer 23

addition proceeds faster than GTP hydrolysis

Question 24

_______ allows the tubule to grow/shrink MT as needed

Answer 24

dynamic instability

Question 25

what do microtubule associating proteins do (MAP?)

Answer 25

bind to free ends of MTs and stabilize ends selectively to polarize a cell

Question 26

what are 2 examples of drugs that can change MT stability?

Answer 26

Colchicine, Taxol

Question 27

how does Colchicine function?

Answer 27

binds to free tubulin to prevent polymerization, things cant add onto the end

Question 28

how does Taxol function?

Answer 28

it prevents loss of subunits from MT

Question 29

what are the 3 classes of MT that make the mitotic spindle?

Answer 29

astral, kinetochore, interpolar

Question 30

________ attach to the kinetochore of condensed chromosomes and tethers them to poles. during anaphase when they shorten, they pull the chromatids apart

Answer 30

kinetochore MT

Question 31

______ are any microtubule originating from the centrosome which does not connect to a kinetochore.

Answer 31

astral MT

Question 32

________ are the antiparallel microtubules that originate from opposite poles, and overlap at the midzone of mitotic spindles.

Answer 32

interpolar MT

Question 33

is a kinetochore actually attached to the end of the microtubule?

Answer 33

no! it has a yoke around it

Question 34

_______ on interpolar MT push poles apart and pull chromatids across poles while _______ on astral MT pull poles toward membranes

Answer 34

kinesins
dyenins