control of the cell cycle Flashcards
Progression through the cell cycle is controlled by what?
Progression through the cell cycle is
controlled by checkpoints
What are the roles of checkpoints in the cell cycle?
Checkpoints are mechanisms within the cell that
- assess the condition of the cell during
the cell cycle
- halt progression to the next phase until certain requirements are met.
What are cyclin proteins? What is their role?
Cyclin proteins that accumulate during cell growth are involved in regulating the cell cycle.
What are the three checkpoints in the cell cycle?
Checkpoints occur at the G1, G2 and metaphase.
Brief description - they are mechanisms within the cell which assess the condition of the cell during the cell cycle and halt progression to the next stage if certain requirements at these checkpoints are not met.
An uncontrolled reduction in the rate of the cell cycle may result in?
An uncontrolled reduction in the rate of the cell cycle may result in degenerative disease
An uncontrolled increase in the rate of the cell cycle may result in?
An uncontrolled increase in the rate of the cell cycle may result in tumour formation.
What is the gene proto-oncogene involved in? what is another fate of this gene?
A proto-oncogene is a normal gene, usually involved in the control of cell growth or division, which can mutate to form a tumour promoting oncogene
What does cyclins combine with? When it combines to form a complex what is its role?
Cyclins combine with and activate cyclin
dependent kinases (CDKs). Active cyclin
CDK complexes phosphorylate proteins that regulate progression through the cycle. If sufficient phosphorylation is reached, progression occurs.
Describe the G1 checkpoint
At the G1 checkpoint, retinoblastoma protein (Rb) acts as a tumour suppressor by inhibiting the transcription of genes that code for proteins needed for DNA replication.
Phosphorylation by G1 cyclin-CDK inhibits the retinoblastoma protein (Rb).
(Phosphorylation by G1 cyclin-CDK inhibits the activity of Rb, meaning that it can no longer bind the transcription factor)
This allows transcription of the genes that code for proteins needed for DNA replication. Cells progress from G1 to S phase.
Describe the G2 checkpoint
At the G2 checkpoint, the success of DNA
replication and any damage to DNA is
assessed.
If there is damage:
DNA damage triggers the activation of
several proteins including p53 that can
stimulate DNA repair, arrest the cell cycle or cause cell death (apoptosis)
What does the metaphase checkpoint controls which stage to which stage?
A metaphase checkpoint controls
progression from metaphase to anaphase.
At the metaphase checkpoint progression is halted until?
At the metaphase checkpoint, progression is halted until the chromosomes are aligned
correctly on the metaphase plate and
attached to the spindle microtubules.
