Unit 1 - Topic 5 - Protein control of cell division - Section C - 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.
Cyclin proteins that accumulate during cell growth are involved in what
Regulating the cell cycle
How are cyclin proteins involved in regulation of the cell cycle
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
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. Phosphorylation by G1 cyclin-CDK inhibits the retinoblastoma protein (Rb)
What does the G1 checkpoint allow
This allows transcription of the genes that code for proteins needed for DNA replication. Cells progress from G1 to S phase.
What happens at checkpoint G2
The success of DNA replication and any damage to DNA is assessed. DNA damage triggers the activation of several proteins including p53 that can stimulate DNA repair, arrest the cell cycle or cause cell death
What does a metaphase checkpoint control
Progression from metaphase to anaphase
What happens at a metaphase checkpoint
Progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle microtubules
What may an uncontrolled reduction in the rate of the cell cycle result in
Degenerative disease
What may an uncontrolled increase in the rate of the cell cycle result in
Tumour formation
What is a proto-oncogene
A normal gene, usually involved in the control of cell growth or division, which can mutate to form a tumour-promoting oncogene
