Interphase

Question 1

What are the stages of interphase in order?

Answer 1

G1, S, G2

Question 2

What occurs during interphase?

Answer 2

• Normal cell functions such as producing hormones and enzymes, protein synthesis occurs in cytoplasm.
• DNA is replicated and checked for errors in the nucleus.
• Mitochondria grow and divide, increasing in number in the cytoplasm.
• Chloroplasts grow and divide in plant and algal cell cytoplasm, increasing in number.
• The normal metabolic processes of cells occur (some, including cell respiration, also occur throughout cell division).

Question 3

What occurs in G1?

Answer 3

• The first growth phase: proteins necessary for organelle production are synthesised, organelles are replicated. The cell increases in size.

Question 4

What does the G1 checkpoint check for?

Answer 4

• cell size
• nutrients
• growth factors
• DNA damage

If a cell satisfies the requirements of the checkpoint it is triggered to begin DNA replication. If not, it enters G0.

Question 5

What occurs during S phase?

Answer 5

• Synthesis phase: DNA is replicated in the nucleus.

Question 6

What occurs during G2?

Answer 6

• Second growth phase: the cell continues to increase in size, energy stores are increased and the duplicated DNA is checked for errors.

Question 7

What does the G2 checkpoint check for?

Answer 7

• Occurs before mitotic phase. DNA checked to have replicated without error. If this checkpoint is passed, the cell initiates the molecular processes that signal the beginning of mitosis.

Question 8

What is the spindle assembly (metaphase) checkpoint?

Answer 8

This checkpoint is at the point in mitosis where all the chromosomes should be attached to spindles and have aligned. Mitosis cannot proceed until this checkpoint is passed.

Question 9

What is G0? Why do cells enter it?

Answer 9

G0 is the phase when a cell leaves the cycle, either temporarily or permanently. There are a number of reasons for this including:
- Differentiation: A cell that becomes specialised to carry out a specific function indefinitely and not enter the cell cycle again.
- The DNA of a cell may be damaged, in which case it is no longer viable. A damaged cell can no longer divide and enters a period of permanent cell arrest (G0). The majority of normal cells only divide a limited number of times and eventually become senescent.
- As a person ages, the number of these cells in their body increases. Linked to many age related diseases.

Question 10

What is the function of checkpoints in the cell cycle?

Answer 10

Control mechanisms of the cell cycle. They monitor and verify whether the processes at each phase of the cell cycle have been accurately completed before the cell is allowed to progress into the next phase.