Unit 1.5c

Question 1

Why are there checkpoints in the cell cycle?

Answer 1

There are checkpoints to assess the cell condition during the process of the cell cycle

Question 2

Why is progression to the next phase halted at checkpoints?

Answer 2

To allow time to check that certain requirements are met.

Question 3

How many checkpoints are there?

Answer 3

There are three checkpoints

Question 4

What/where are the three checkpoints?

Answer 4

1. Near the end of G1
2. At the end of G2
3. During metaphase in the mitotic phase

Question 5

What are cyclin proteins?

Answer 5

Cyclin proteins are proteins that accumulate during cell growth and are involved in regulating the cell cycle

Question 6

What do you cyclin proteins combine with and activate?

Answer 6

cyclin-CDKs

Question 7

What does cyclin-CDKs stand for?

Answer 7

cyclin-dependant kinases

Question 8

What do the active cyclic-CDKs complexes phosphorylate?

Answer 8

Proteins that regulate progression through the cell cycle

Question 9

What does sufficient phosphorylation mean?

Answer 9

Sufficient phosphorylation means the cell cycle can progress

Question 10

What does insufficient phosphorylation mean?

Answer 10

It means the cell cycle is stopped

Question 11

G1 Checkpoint - what is retinoblastoma protein and what is it shortened to?

Answer 11

Retinoblastoma protein (Rb)
It’s a tumour suppressor

Question 12

G1 Checkpoint - What does Rb do?

Answer 12

It inhibits gene transcription which codes for proteins needed in DNA replication

Question 13

G1 Checkpoint - What inhibits Rb?

Answer 13

G1 cyclin-CDKs

Question 14

G1 Checkpoint - What does the inhibition of Rb result in?

Answer 14

It means that the transcription of genes coding for proteins needed in DNA replication can take place

Question 15

G2 Checkpoint - What is assessed here?

Answer 15

The success of DNA replication and any damage to DNA

Question 16

G2 Checkpoint - What does DNA damage trigger?

Answer 16

The activation of the p53 protein

Question 17

G2 Checkpoint - What three things can the activation of the p53 protein cause?

Answer 17

1. Stimulation of DNA repair
2. Arrest of the cell cycle
3. Initiation of cell death

Question 18

G2 Checkpoint - What is another word which can be used for the initiation of cell death?

Answer 18

Apoptosis

Question 19

M Checkpoint - what does this checkpoint control?

Answer 19

It controls the progression from metaphase to anaphase

Question 20

M Checkpoint - What is this phase conditional on?

Answer 20

Set the chromosomes are aligned correctly on the metaphase plate, and the spindle microtubules are attached