Cell division

Question 1

How can you identify which stage of the cycle a cell is in?

Answer 1

Analysis of DNA content of an asynchronous population by flow cytometry

Question 2

Regulation of the cell cycle
key points is focused primarily at …?

Answer 2

at G1/S and G2/M transition. Relies on transient activation of a protein kinase complex (Cdk-cyclin) allowing progression through the cell cycle

Question 3

cdk (cyclin dependant kinases) have subunits with ??? activity

Answer 3

Subunit with ser/thr kinase activity

Question 4

Cyclins are a ??? subunit that attach to cdks to form a complex

Answer 4

regulatory subunit (concentration rises and falls)

Question 5

TRUE OR FALSE: cell cycle regulation in fission yeast has two cyclins or two cdks? and only one of the other.

Answer 5

two cyclin types, a G1 phase cyclin, and a M phase cyclin, only one cdk known as cdc2 in yeast

Question 6

are all cdk-cyclin complexes stimulatory?

Answer 6

No, not all cdk-cyclins are stimulatory
e.g. cyclinB1-Cdk1 has inhibitory function in G2 – prevents cells from rereplicating DNA

Question 7

For cells to pass through a point of commitment (i.e checkpoints) Cdks must be transiently activated by specific ???

Answer 7

cyclins.

Question 8

checkpoint at ??? checks whether Mitogenic signal has been received.

Answer 8

G1 to S phase checkpoint

Question 9

If mitogenic signal has been received at G1-S phase checkpoint, what happens?

Answer 9

DNA synthesis machinery is triggered

Question 10

TRUE or FALSE: if a mitogenic signal is not received at G1-S checkpoint, the cell doesn’t go into G0 phase i.e. terminal differentation

Answer 10

FALSE, it DOES go into Go

Question 11

terminal differentiation time of cell spent in this phase varies. some cells like ??? never go into this phase as they are constantly differentiating/replicating/growing whilst others like ??? stay for a long time in G0

Answer 11

stem cells cells
neurons and RBCs

Question 12

the checkpoint at ??? checks whether cell is big enough and whether DNA is replicated and undamaged

Answer 12

S-G2 checkpoint

Question 13

passing the S-G2 checkpoint triggers ??? machinery

Answer 13

mitosis machinery

Question 14

TRUE or FALSE: G2 is shorter than G1 and less variable due to its activity metabolically (glucose oxidation,
replication, transcription, translation)

Answer 14

TRUE

Question 15

external factors such as ??? stimulate a cell to divide or not

Answer 15

cytokines, growth factors

Question 16

at what stage do Centrosomes duplicate and Chromosomes start to
condense? Also cytoskeleton disassembles

Answer 16

G2 phase

Question 17

at what stage does DNA get replicated and histones produced in higher quantities?

Answer 17

S ohase

Question 18

at what stage of cell division do organelles get duplicated and cell grows normally and metabolism is normal?

Answer 18

G1 phase

Question 19

Analysis of DNA content of an asynchronous population by flow cytometry reveals ???

Answer 19

which stage of the cell cycle a cell is in

Question 20

Regulation of the cell cycle relies on transiently activated ??? which then allows progression through cycle

Answer 20

cdk-cyclin complex

Question 21

TRUE or FALSE: Specificity of cdk action depends on type of associated cyclin binding to it

Answer 21

TRUE
Eg., nuclear lamins&raquo_space; nuclear-envelope breakdown
Other proteins&raquo_space; changes in organisation of chromosome and cytoskeleton

Question 22

1. cyclin binding to cdk causes conformational change that allows the active site to be exposed. The active cdk can then ??? other proteins

Answer 22

phosphorylate

Question 23

2. cyclin and cdk synthesis is important for commitment to enter cell cycle e.g. yeast divides until ???

Answer 23

negative nutrient signal is received. In eukaryotes this is growth factors

Question 24

2. steps of synthesis involve:
3. growth factor binding to RTK =
4. activation of Ras =
5. activation of ??? pathway
6. activates produciton of jun and fos (nuclear transcription factors
7. ???

Answer 24

3. MAPK
4. synthesis of G1 cyclins and cdks

Question 25

example of steps of cdk and cyclin synthesis is the:
G1 cdk-cyclin complex regulates progression through constriction point by ??? Rb protein which binds E2F (transcription factor)

Answer 25

phosphorylating

Question 26

when Rb is phosphorylated and binds to E2F, transcription occurs or does not occur?

Answer 26

does not occur. Only occurs once Rb releases E2F upon phosphorylation by protein kinases

Question 27

3. controlled proteolysis via the ???

Answer 27

ubiquitin-proteasome pathway

Question 28

3. proteolysis of cdks and cyclins involves two types of ubiquitin ligase:
4. ??? (active in mitosis, targets mitotic cyclin = cell exits mitosis)
5. SCF complex (active from late G1, targets ??? cyclins)

Answer 28

1. anaphase promoting complex
2. G1 cyclins

Question 29

Active mitotic Cdk-cyclin stimulates:
1. Nuclear envelope breakdown
2. Chromosome condensation
3. ??? formation
4. Targeted protein degradation

Answer 29

Mitotic spindle

Question 30

4. control of cdk activity by regulation by inhibitory phosphorylation:
   - Y15-P = ??? until phosphotase comes along to remove phosphate group
   - T161-P = ???

Answer 30

Y15-P = inhibitory
T161-P = activatory

Question 31

5. subcellular localisation:
   e.g. Cyclin B1-GFP is in cytoplasm and not allowed into ??? until it is needed. This is via control of gates/shuttles across membrane/envelope

Answer 31

nucleus where it has its effect

Question 32

6. Checkpoints, Cdk Inhibitors, and
   Cellular Responses: Progress through the cell cycle can be arrested
   at a checkpoint by:
   * Sensors that detect ???
   * Transmitters that signal the information.
   * Effectors that inhibit cell cycle machinery. (Eg CdK inhibitors)

Answer 32

chromosomal abnormalities

Question 33

ATM gene generates ATM protein which repairs dsDNA breakage from ??? but when mutated does not = many dsDNA breaks

Answer 33

ionising radiation