Control Of Cell Proliferation

Question 1

What are the phases of cell cycle

Answer 1

G1
S phase
G2
M phase (mitosis and cytokinesis)

Question 2

What is the G1 phase

Answer 2

Deciding whether conditions (extracellular environment/ intracellular environments/nutrients) are optimal for division

1. Cell produces proteins for organelle synthesis
2. Replicates cell organelles
3. Cell increases in size

Question 3

S phase?

Answer 3

DNA replication semi conservative

Question 4

G2 phase?

Answer 4

organelles duplicate
Cytoplasm and Cell membrane grows
Energy stores increased

Question 5

Checkpoints in the cell cycle

Answer 5

G1 checkpoint - is environment favourable
G1/S - dna integrity
G2 checkpoint - ensures da replication successful
Metaphase checkpoint - chromosome distribution equally. Ensures all chromosomes attached.

Question 6

What is quiescence

Answer 6

When cell is not dividing
State of most cells
Growth factors not present

Question 7

Extracellular signals that influence G1 checkpoint

Answer 7

Unfavourable extracellular environment:
Growth factors
Growth inhibitory proteins
Nutrient status

Question 8

What are Cdks

Answer 8

“Cyclin dependent kinases”
Enzymes that regulate cell cycle checkpoint transition
(G1 AND G2)
Regulated by feedback
Effect the rate of cell cycle persist in cell as inactive forms until cyclin resynthesized during interphase

Question 9

What is a kinase

Answer 9

Enzymes that activates/ deactivates a protein by phosphorylating them

Question 10

What is the role of cyclin

Answer 10

Activate Cdk
Cyclically fluctuate in conc in the cell cycle. Growth factors increase amount of cyclin.
When cyclin degrades Cdk inactivate

Question 11

What is M-Cdk and its role in the cell cycle

Answer 11

By G2 checkpoint enough cyclin is available to form M-Cdk
- “Maturation promoting factor”
Complex initiates mitosis
M-Cdk switches itself off by initiating a process which leads to destruction of cyclin

Question 12

What is pRB retinoblastoma protein

Answer 12

Tumour suppressor protein
Regulates G1 restriction point
PRB normally inhibits a transcription factor (which starts cell cycle)

When GF present active Cdk phosphorylates pRB
PRB released from TF allowing cell cycle to progress

Question 13

P53?

Answer 13

Regulates dna damage checkpoint G1/S

Dna damage causes an increase in p53
Activates p21 an inhibitor of Cdk
Prevent continuation into S phase giving time for dna to repair

Severe dna damage induces cell to kil itself - apoptosis

Question 14

Apoptosis?

Answer 14

Cell kills itself

Question 15

Consequences of checkpoint failure

Answer 15

Proliferation of cells in absence of GF
Replication of damaged dna
Segregation of incompletely replicated chromosomes
Division of cells with wrong number of chromosomes

Question 16

Oncogenic?

Answer 16

Involved in the origin or development of tumours or cancer

Question 17

What factors in cell cycle can become oncogenic

Answer 17

Receptors (Her2) - mutated, constitutively active or over expressed
Signalling proteins (ras protein) - most common oncogene
Regulatory proteins - over expression of myc TF

Question 18

What is Ras protein?

Answer 18

A type of signalling protein known as a molecular switch

Question 19

What is interphase

Answer 19

G1
S
G2

Question 20

Kinetochore?

Answer 20

Protein complex at each centromere which serves as attachment site for spindle microtubules

Question 21

G1 checkpoint?

Answer 21

Regulated by pRB
Ensures cell large enough to divide and enough nutrients/ GF If cell doesn’t have go ahead - switches to G0

Question 22

G1/ S checkpoint?

Answer 22

Checks original dna integrity
Apoptosis to ensure damaged dna not passed on

Question 23

G2 checkpoint?

Answer 23

ensures DNA replication in S phase has been successful
apoptosis occurs if stop signal is received

Question 24

Metaphase checkpoint?

Answer 24

ensures that all of the chromosomes are attached to spindle by their kinetochore
ensure equal amounts of chromatin are going to each daughter cell