Control of Cell Proliferation Flashcards
Stages of cell cycle
- G1 (growth) phase
- S (synthesis) phase
- G2 phase
- M (mitosis) phase
What is the G1 restriction point?
The point at which the cell commits to the cell cycle and no longer requires signals to complete it
What happens at the G1 restriction point?
Cell either enters cycle or becomes quiescent
What checkpoints are there?
- G1/S
- G2/M
- M
What happens at the G1/S checkpoint?
Checks for DNA damage
What happens at the G2/M checkpoint?
Checks if DNA hasn’t been replicated properly or is damaged
What happens at the M checkpoint?
Checks if there is spindle attachment failure
What enzymes regulate the cell cycle?
Cyclin dependent kinases (Cdks)
What are the 3 major Cdks and what are their functions?
- G1 Cdk = gets cell past restriction point
- G1/S Cdk = gets cell into S phase
- M Cdk = gets cell into M phase
What activate Cdks?
Cyclins
What are cyclins?
Proteins that cyclically fluctuate in concentration throughout the cycle
What are the 4 cyclins?
- Cyclin A
- Cyclin B
- Cyclin E
- Nuclear D1
How do cyclins allow mitosis to initiate?
- Cyclins accumulate in the G1, S and G2 phases
- By end of G2 enough is available to form M-Cdk complexes which initiate mitosis
What type of gene is retinoblastoma protein (pRB)?
Tumour suppressor gene
Function of pRB
Inhibits a transcription factor which promotes entry into cell cycle
