The cell cycle

Question 1

What are the 3 stages of a cell cycle?

Answer 1

• Interphase - which occupies most of the cell cycle, sometimes known as the resting phase because no division takes place.
• Nuclear division - When the nucleus divides into 2 (mitosis) or 4 (meiosis).
• Division of the cytoplasm (cytokinesis) - It follows on from nuclear division, the cytoplasm divides and produces 2 or 4 new cells.

Question 2

How long does a cell cycle take?

Answer 2

It varies between organisms, but a mammalian cell can take up to 24hrs and 90% is interphase.

Question 3

What is cancer?

Answer 3

• A group of disease caused by growth disorder of cells, it’s the result of damage to the genes that regulate cell cycle and mitosis.

Question 4

What happens to the cells when cancer begins?

Answer 4

• The cells divide uncontrollably, as a result, a group of abnormal cells (tumours) develops and constantly expand in size.

Question 5

Where can tumors be found?

Answer 5

• Can develop in any organ of the body, most commonly found in the lungs, prostate gland (male), breast and ovaries (female), large intestine, stomach, oesophagus, and pancreas.
  A tumor becomes cancerous when it changes from benign to malignant.

Question 6

How can a mutation disruption mitosis?

Answer 6

• A mutation to one of these genes can cause uncontrolled mitosis.
• Mutant cells are structurally and functionally different from normal cells.
• Most mutant cells die but the ones that survive can form clones and form tumours.
• Malignant tumours grow rapidly, less compact and are more likely to be life-threatening.
• Benign one grows more slowly, more compact and are less likely to be life-threatening.

Question 7

What’s the general idea to treat cancer?

Answer 7

• Often involves killing dividing cells by blocking a part of the cell cycle.
• Then the cell cycle is disrupted and cell division hence cancer growth.

Question 8

How can drugs e.g. Chemotherapy treat cancer?

Answer 8

• It disrupts the cell cycle by:
• Preventing DNA from replicating.
• Stops metaphase stage of mitosis by interfering with spindle formation.

Question 9

What is the problem of drugs that treats cancer?

Answer 9

• It can also disrupt the cell cycle of normal cells.
• However, as cancer have a particularly fast rate of division and they are more damaged than normal cells, therefore, drugs are more effective against rapidly dividing cells.
• Normal body cells e.g. hair cells, that divide rapidly are also vulnerable to the damage, explains the hair loss during chemotherapy treatment.