Biology 2.7 Cell Cycle

Question 1

What are the stages of the cell cycle?

Answer 1

• Growth 1
• Synthesis
• Growth 2
• Mitosis and Cytokinesis
• Resting

Question 2

What is the cell cycle?

Answer 2

The cell cycle describes the ‘life cycle of a cell’. it is a series of events that take place as cells grow and divide via mitosis.

Question 3

What happens in the G1 phase?

Answer 3

The cell grows physically larger, duplicates some organelles, and makes building blocks and proteins in prep for DNA replication.

Question 4

What happens in the G1 checkpoint and when does this occur?

Answer 4

This occurs late in the G1phase of the cell cycle. This checks for cell size, growth factors, DNA damage and required proteins.

Question 5

What happens in the S phase?

Answer 5

The cell replicates a complete copy of DNA (synthesises) and copies the centrosome (involved in spindle formation in metaphase).

Question 6

What happens in the G2 phase?

Answer 6

The cell grows more, duplicates some organelles, synthesises proteins needed in mitosis and dismantles the cytoskeletion.

Question 7

What happens in the G2 checkpoint and when does this occur?

Answer 7

This occurs late in the G2 phase of the cell cycle. This checks for correct DNA replication.

Question 8

What happens in the M phase?

Answer 8

The cell undergoes mitosis (separation of DNA) and undergoes cytokinesis (separation of the cytoplasm).

Question 9

What happens in the M checkpoint and when does this occurs?

Answer 9

This occurs in the metaphase stage which is the middle of the mitosis phase of the cell cycle. This checks that the spindle has attached to all sister chromatids.

Question 10

What happens in the G0 phase?

Answer 10

Some cells may exit the G1 phase and enter a resting state known as G0. During the resting state, the cell is not actively preparing to divide, its just doing its job.

Question 11

What are some examples of the cell cycle regulation?

Answer 11

1. Human Growth Hormone
   - This growth-promoting hormone can initiate cell division. (Too much HGH = Gigantism)
   - A lack of the hormone can inhibit cell division. (Too little HGH = Dwarfism)
2. Testosterone and Thyroxine
   - Stimulates division in several cell types.
3. Cytokinin
   - A hormone found in plants that promotes cell division.

Question 12

What is cell cycle requlation?

Answer 12

Hormones can externally regulate the cell cycle.