1x- Control of the cell cycle Flashcards
What is progression through the cell cycle controlled by?
Checkpoints
What are checkpoints?
Mechanisms within the cell that assess the condition of the cell during the cell cycle and halt progression to the next phase until certain requirements are met
What are cyclin proteins that accumulate during cell growth involved in?
Regulating the cell cycle
What do cyclins combine with and activate?
Cyclin-dependent kinases (CDKs)
What do active cyclin-CDK complexes do?
Phosphorylate proteins that regulate progression through the cycle. If sufficient phosphorylation is reached, progression occurs
What happens 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
What inhibits the retinoblastoma protein (Rb)?
Phosphorylation by G1 cyclin-CDK
What happens at the G2 checkpoint?
The success of DNA replication and any damage to DNA is assessed
What does the inhibition of retinoblastoma protein (Rb) allow for?
The transcription of the genes that code for proteins needed for DNA replication. This means cells can progress from G1 to S phase
What does DNA damage trigger the activation of?
Several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death
What does the metaphase checkpoint control?
Progression from metaphase to anaphase
What happens at the metaphase checkpoint?
Progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules
What may a uncontrolled reduction in the rate of the cell cycle result in?
Degenerative disease
What may a uncontrolled increase in the rate of the cell cycle result in?
Tumour formation
What is a proto-ongonene?
A normal gene, usually involved in the control of cell growth or division, which can mutate to form a tumour-promoting oncogene
