The Cell Cycle And Its Regulation

Question 1

What are the purpose of the checkpoints in interphase?

Answer 1

To prevent uncontrolled division that would lead to tumours.

To detect and repair damage to DNA e.g. Damage caused by UV light.

Question 2

What else do the phases of interphase ensure?

Answer 2

The cycle cannot be reversed.

The DNA I only duplicated once during each cycle.

Question 3

What happens in M phase?

Answer 3

Cell growth stops.
Nuclear division consisting of prophase, metaphase, anaphase and telophase.
Cytokinesis (cytoplasmic division)

Question 4

What happens in G0 phase?

Answer 4

Cells undergo programmed cell death, differentiation or senescence (cell deterioration).

Question 5

What happens in the G1 phase?

Answer 5

Cells grow and increase in size.
Transcription of genes to make RNA.
Organelles duplicate
Biosynthesis eg protein synthesis
The p53 tumour suppressor gene helps to control this phase

Question 6

What happens in the S phase?

Answer 6

DNA replicates

This phase is rapid

Question 7

What happens in the G2 phase?

Answer 7

Cells grow

Question 8

Is there a specific order to what parts of the DNA are replicated first?

Answer 8

Yes. The house keeping genes (that every cells has) are first. The genes that are normally inactive are duplicated last.

Question 9

How is a cell checked if it is ready for mitosis?

Answer 9

Special chemicals in the G2 phase check the ability of proteins that will be involved in making chromosomes condense and in the formation of the spindle.