1.5c Control of the Cell Cycle

Question 1

What is progression through the cell cycle controlled by?

Answer 1

checkpoints

Question 2

What are checkpoints?

Answer 2

-Mechanisms withing 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

Question 3

What do cyclin proteins do and where do they come from?

Answer 3

• they are proteins that accumulate during cell growth
• involved in regulating the cell cycle

Question 4

How do cyclin proteins regulate the cell cycle?

Answer 4

• Cyclins combine with active cyclin-depndant kinases (CDKs)
• Active cyclin-CDK complexes phosphorylate proteins that regulate progression through the cycle
• If sufficient phosphorylation is reached. progression occurs

Question 5

What happens at the G1 checkpoint?

Answer 5

• Retinoblastoma protein (Rb) acts as a tumour supressor by inhibiting the transcription of genes that code for proteins needed for DNA replication
• Phosphorylation by G1 cyclin-CDK inhibits the retinoblastoma protein (Rb)
• this allows transcription of the genes that code for proteins needed for DNA replication. Cells progress from G1 to S phase

Question 6

What happens at the G2 checkpoint?

Answer 6

• The success of DNA replication and and 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

Question 7

What happens at the metaphase checkpoint

Answer 7

• Controls to progression from metaphase to anaphase
• Progression is halted until the chromosomes are aligned correctly on the metaphase plate and attached to the spindle micotubules

Question 8

What may cause degenerative disease?

Answer 8

an uncontrolled reduction in the rate of cell cycle

Question 9

What may lead to tumour formation?

Answer 9

an uncontrolled increase in the rate of cell cycle