6.1 - The Cell Cycle

Question 1

What are the phases of the cell cycle?

Answer 1

Interphase and Mitotic Division

Question 2

What does interphase consist of?

Answer 2

• DNA is replicated and checked for errors in the nucleus
• Protein synthesis occurs in the cytoplasm
• Mitochondria/Chloroplasts grow + divide and increase in numbers
• Normal Metabolic processes of cells

Question 3

What are the three stages of interphase?

Answer 3

• G1: proteins which produce organelles are produced and organelles replicate. The cell gets bigger.
• S: DNA is replicated in the nucleus
• G2: The cell gets bigger, energy stores increase, and the DNA duplicated is checked for errors

Question 4

What is the mitotic phase and what does it consist of?

Answer 4

It is the period of cell division and consists of:

• Mitosis: the nucleus divides
• Cytokinesis: the cytoplasm divides and two cells are produced

Question 5

What is G0? Why does it happen?

Answer 5

It is when the cell leaves the cycle.
It can occur when:
- The cell becomes differentiated: A cell that is differentiated can no longer divide, and cannot enter the cell cycle
- The DNA of a cell is damaged: it can no longer divide and enters a period of permanent cell arrest + become senescent
- Old age: too many senescent cells in the body and can lead to cancer or arthritis

Question 6

What are the checkpoints in the Cell Cycle?

Answer 6

G1: towards the end, checks for:
- Cell Size
- DNA Damage
- Nutrients 
- Growth factors 
If it doesn’t satisfy everything, it goes to G0
G2: towards the end, checks for:
- DNA Replication
- Cell size
- DNA damage
Spindle assembly checkpoint (metaphase checkpoint):
- Checks if chromosomes are attached to spindles and have aligned