cell cycle

Question 1

what do centrosomes consist of

Answer 1

pairs of centrioles, made of triplets of microtubules

Question 2

what do microtubules do?

Answer 2

radiate out from centrosome and attach to chromosome

Question 3

what happens as microtubules grow and shrink?

Answer 3

chromosomes are pulled to the poles

Question 4

what are many microtubules called?

Answer 4

k fibres (kinetochore fibres)

Question 5

alpha-tubulin

Answer 5

dimer that makes up microtubules

Question 6

beta-tubulin

Answer 6

dimer that makes up microtubules

Question 7

kinetochore

Answer 7

made of many proteins, forms on the mitotic chromosomes adjacent to the centromeres allowing microtubules to bind

Question 8

prophase

Answer 8

chromosomes condense and envelope breaks down, centrosomes start to migrate and make microtubules

Question 9

prometaphase

Answer 9

chromosomes fully condensed but not aligned, NE fully digested, microtubule capture, centrioles position

Question 10

metaphase

Answer 10

chromosomes aligned at plate, amphitelic microtubule attachment, CHECKPOINT

Question 11

what does amphitelic microtubule attachment mean?

Answer 11

microtubules have captured chromosomes equally on either side

Question 12

anaphase

Answer 12

sister chromatids detach and move towards poles

Question 13

telophase/cytokinesis

Answer 13

NE reforms, chromosomes decondense, cleavage furrow

Question 14

what is cleavage furrow?

Answer 14

the pinching in the centre of the cell when it splits

Question 15

lagging chromosome

Answer 15

when one chromosome goes to wrong cell because of incorrect microtubule attachment

Question 16

what is the correct type of microtubule attachment?

Answer 16

amphitelic attachment

Question 17

syntelic attachment

Answer 17

microtubules from one side attaches to both

Question 18

monotelic attachment

Answer 18

microtubules only attach on one of the sides

Question 19

merotelic attachment

Answer 19

bipolar attachment with another from one side

Question 20

what do the wrong attachments of microtubules result in

Answer 20

unequal forces and therefore a lagging chromosome

Question 21

what happens when attachment of microtubules goes wrong

Answer 21

polyploidy

Question 22

polyploidy

Answer 22

abnormal number of chromosomes

Question 23

describe G1

Answer 23

highly metabolically active, cell growth, duplication of organelles (8-10 hrs)

Question 24

describe S phase

Answer 24

DNA replication, centrosome duplication (6-8hrs)

Question 25

Describe G2

Answer 25

more cell growth, accumulation of key enzymes needed to trigger entry into mitosis, cytoskeleton preps for remodelling required in cell division

Question 26

how does a CDK work

Answer 26

it bind to a cyclin and then it can phosphorylate

Question 27

what do CDKs and cylins do to the cell cycle?

Answer 27

pushes it forward

Question 28

how does a CDK-cyclin complex activate a target protein?

Answer 28

phosphorylates it

Question 29

what happens after CDK-cyclin complex activates the target protein?

Answer 29

it disperses and can no longer activate proteins

Question 30

what is a PTM

Answer 30

post-translational modification

Question 31

what phase is cyclin D in

Answer 31

G1

Question 32

what phase is cyclin E in

Answer 32

G1/S

Question 33

what phase is cyclin A in

Answer 33

S/G2

Question 34

what phase is cyclin B in

Answer 34

M

Question 35

what phase are CDK 6 and 4 in

Answer 35

G1

Question 36

what phase is CDK 2 in

Answer 36

S

Question 37

what phase is CDK 1 in

Answer 37

G2/M

Question 38

what happens at G1/S checkpoint

Answer 38

DNA damage checkpoint, if there is DNA damage the cell cycle stops

Question 39

what happens at G2/M checkpoint

Answer 39

DNA damage checkpoint

Question 40

what happens at M checkpoint

Answer 40

spindle assembly checkpoint

Question 41

what do DNA damage checkpoints do

Answer 41

sense for 'favourable conditions' cell size, growth factors and DNA damage

Question 42

what happens if DNA damage is detected

Answer 42

increase in P53 and P21

Question 43

what does P21 do

Answer 43

inhibits CDKs which leads to cell cycle arrest or apoptosis

Question 44

what happens at a spindle assembly checkpoint

Answer 44

BubR1 sits on kinetochore until microtubules are stably attached, it leaves and then activates the Anaphase Promoting Complex (APC), APC releases separase which cuts the sister chromatids ONLY if there is proper microtubule attachment

Question 45

example of mutations to key regulators - BubR1 gene

Answer 45

aberrant checkpoint signalling promotes cells with abnormal number of chromosomes leading to cancer

Question 46

example of mutations to key regulators - retinoblastoma (Rb)

Answer 46

CDK phosphorylates Rb, E2F transcription factor released by Rb, if mutated then too much E2F released, too many cyclins are produced so cell cycle is no longer controlled

Question 47

what shape are cells in interphase and what shape are mitotic cells

Answer 47

interphase - flat, mitotic - round

Question 48

what do centrosomes do

Answer 48

radiate microtubules

Question 49

what are multipolar spindles

Answer 49

microtubules attach in many different directions due to the cell having 3 centrosomes so 3 cells form

Question 50

what happens in G0

Answer 50

many cells differentiate and exit the cell cycle

Question 51

Cell cycle control - example of targets (Rb and E2F)

Answer 51

after mitosis growth factors are expressed as well as cyclin D and CDK 4&6, Rb binds to E2F (TF) and holds it if inactive. CDK cyclin complexes phospho's Rb, E2F goes to nucleus for transcription - Cyclin E is produced