Cell Replication

Question 1

In the absence of stimulus what section of the cell cycle do cells enter

Answer 1

G0

Question 2

Why do cells leave G0 (process)

Answer 2

Signalling cascade;
Response to extra cellular factors
Signal amplification
Signal integration/modulation by other pathways

Question 3

c-Myc

Answer 3

A transcription factor which stimulates the expression of cell cycle genes
Promotes G0 to G1
c-Myc is an oncogene (overexpressed in tumours)

Question 4

What do Cyclin dependant kinases (CDKs) do

Answer 4

(De)&Phosphorylation of cyclin
Involved in key signalling events

Question 5

In what state of cells are CDKs present

Answer 5

Proliferating/mitosis

Question 6

In what state are CDKs active

Answer 6

Only when cyclin is bound

Question 7

What checkpoints arrest the cell cycle in G1

Answer 7

Damaged DNA
Unfavourable extracellular environment

Question 8

What checkpoints arrest the cell cycle in S

Answer 8

Damaged or incorrectly replicated DNA

Question 9

What checkpoints arrest the cell cycle in G2

Answer 9

Damaged or incorrectly replicated DNA

Question 10

What checkpoints arrest the cell cycle in M

Answer 10

Chromosome improperly attaches to mitotic spindle

Question 11

Cell.cycle entry requirements

Answer 11

Growth factor - c-Myc- cyclin D - cdk complex

Question 12

Frequently the protein regulated by a kinase is

Answer 12

Another kinase

Question 13

This cascade of kinases allows for

Answer 13

Signal amplification
Diversification
Opportunity for regulation

Question 14

Cyclins are expressed

Answer 14

Transiently at specific points of the cell cycle

Question 15

What regulates cdk activity

Answer 15

Interaction w cyclins
Phosphorylation

Question 16

What regulates cyclins

Answer 16

Level of expression

Question 17

Lifecycle of cyclins

Answer 17

Synthesised then Degraded

Question 18

How do cdks give direction and timing to cell cycle

Answer 18

They become sequentially active and stimulate synthesis of genes required for the next phase

Question 19

Cyclins are susceptible to degradation hence

Answer 19

Cyclic activation

Question 20

Retinoblastoma pathology

Answer 20

Rb protein inactive or missing
A tumour suppressor abundant in all nucleated cells

Question 21

How do cells double in size to progress

Answer 21

Intracellular signalling pathways drive protein synthesis
Protein degradation is inhibited

Question 22

Rb function

Answer 22

Inactivates a TF needed for cell cycle progression

Question 23

What happens to Rb in a proliferating cell

Answer 23

Production of G1-Cdk and G1/S-Cdk complexes cause phosphorylation of Rn rendering it inactive hence allowing release of the TF

Question 24

What does the E2F family of TFs do

Answer 24

Regulates the expression of several genes needed for cell cycle progression

Question 25

p53 description

Answer 25

TF which is activated by DNA damage Arrests cells with damaged DNA in G1

Question 26

P53 mechanism

Answer 26

Binds and upregulates p21 gene P21 family members are inhibitors of cyclin;CDK complexes

Question 27

Oncogenes

Answer 27

EGFR/HER2 mutationally activated of over expressed in breast cancers Herceptin antibody for the treatment of HER2+ metastatic breast cancer Ras mutationally activated in many cancers Cyclin D1 overexpressed in 50% of breast cancers C-Myc overexpressed in many tumours

Question 28

Tumour suppressors

Answer 28

Rb loss of function mutations in 80% of small cell lung cancers p53 loss of function mutations in over 50% of all human cancers