Control of the Cell Cycle

Question 1

What is the cell cycle controlled by?

Answer 1

Chechpoints

Question 2

What are the checkpoints?

Answer 2

These checkpoints are mechanisms within the cell that assess if it is ready to move onto the next stage

Question 3

What can checkpoints do?

Answer 3

They can halt the process if they have to

Question 4

What are cyclins?

Answer 4

Proteins

Question 5

Why are cyclin important?

Answer 5

They ensure that cell division is completed

Question 6

When are cyclin proteins are produced?

Answer 6

As the cell nears a checkpoint if everything is okay

Question 7

What happens once cyclins have been produced?

Answer 7

They combine with and activate cyclin-dependent kinases (CDKs).

Question 8

What does CDK regulate?

Answer 8

An active CDK phosphorylates proteins that regulate progression

Question 9

What does the cycle need to be able to progress?

Answer 9

Sufficient phosphorylation

Question 10

What happens at the G1 checkpoint?

Answer 10

Retinoblastoma protein (Rb) acts as a tumor suppressor

Question 11

How does the G1 checkpoint work?

Answer 11

By inhibiting the transcription of genes needed of DNA replication (DNA helicase and DNA polymerase)

Question 12

Give a summary of the G1 checkpoint

Answer 12

Phosphorylation by G1 CDKs inhibits Rb, allowing transcription to occur

Question 13

What happens at the G2 checkpoint?

Answer 13

The success of DNA replication and any damage to DNA is assessed

Question 14

What happens if there is an issue at the G2 checkpoint?

Answer 14

It triggers the activation of different proteins, one being p53

Question 15

What can p53 do in the G2 checkpoint?

Answer 15

It can stimulate DNA repair, stop the cell cycle of even cause cell death

Question 16

What happens at the metaphase checkpoint?

Answer 16

This checkpoint controls the progression from metaphase to anaphase

Question 17

What does the metaphase checkpoint ensure?

Answer 17

It ensures that all the chromosomes are aligned on the metaphase plate and are attached to spindle microtubules

Question 18

What are the 2 possible outcomes if the checkpoints fail?

Answer 18

An uncontrolled reduction in the rate of cell cycle results in a degenerative disease (e.g. Huntington’s)

An uncontrolled increase in the rate of the cell cycle may result in a turmour forming.

Question 19

What gene usually controls cell division?

Answer 19

Protooncogene

Question 20

What happens if P mutates?

Answer 20

Then it can form a tumour-promoting oncogene leading to cancer