19 & 20 - Cell Cycle Control 1 & 2 Flashcards
Events of cell cycle
- G0
- G1
- S
- G2
- M
G0
Terminally differentiated cells withdraw from cell cycle indefinitely
G1 phase
RNA and protein synthesis. No DNA synthesis. Length depends on external conditions
Restriction point
A cell that passes this point is committed to pass into S phase
S phase
DNA synthesis. Doubles amount of DNA in cell. RNA and protein synthesis
G2 phase
No DNA synthesis. RNA and protein synthesis continue.
M Phase
Mitosis and cytokinesis yielding 2 daughter cells
Mid g1 cyclin-CDKs
- Cyclin D-CDK4
- Cyclin D-CDK6
Late g1 cyclin CDKs
- Cyclin E-CDK2
S phase cyclin CDKs
- Cyclin A-CDK2
Mitotic cyclin-CDKs
- Cyclin A-CDK1
- Cyclin B-CDK1
G1 checkpoint
Is environment favourable?
G2 checkpoint
Is all DNA replicated and all DNA damage repaired?
Mitosis Checkpoint
Are all chromosomes properly attached to the mitotic spindle?
Early Response genes
Transcription factors that turn on expression of delayed response genes
Effect of cancer promoting mutations
- Increase ability of cell to proliferate
- Decrease susceptibility of cell to apoptosis
- Increase general mutation rate in cell
- Increase cells longevity
Oncogene mutations
Mutation only required in one allele for tumour formation. The gene in its normal unmutated form = proto-ongogene
Tumour suppressor gene mutations
For cancer to occur, both alleles of gene must be mutated and have no activity
Retrovirus
Cause cancer by mutating and rearranging proto-ongogenes. Insert strong promoters near proto-oncogenes
p53
Tumour suppressor protein that up-regulates expression of specific proteins. Detects damaged DNA in the G1 phase, activates the expression of p21 amd reduces the frequency of mutations in the cell.
Rb
Sequesters the transcription factor E2F which is required for cell cycle progression.
What drives apoptosis
the activity of cysteine-containing aspartate-specific proteases.
