2.2.4: Cancer

What does cancer do?

Cancers cause the genes that control cell divison to mutate, if the mutated gene is one that causes cancer, it is referred to as an oncogene

What happens with most mutations?

• They are not cancerous

• They often result in early cell death or the cell being destroyed by the body’s immune system

• As most cells can be easily replaced, these events often have no harmful effect on the body

Many cancer treatments are focussed on controlling the rate of ____ ____ since the growth of cancer and tumours is an uncontrolled process .

Cell division

What is soemthing that causes cancer called?

A carcinogen

What are the steps of cancer developing (8)?

1. Oncogenes arise due to carcinogens

2. Cancerous cell does not respond to signals from other cells so continues to divide

3. Mitosis

4. Cwancerous cells not removed by the immune system

5. Rapid mitosis

6. Tumour gets bigger

7. Tumour is supplied with blood and lymph vessels. If it is a malignant tumour, tumour cells spread in blood and lymph nodes to other parts of the body.

8. Metastasis. Tumour cells invade other tissues, secondary cancers form throughout the body

What are the 3 checkpoints in the cell cycle?

(1) Cell growth checkpoint

• occurs at the end of growth phase 1 (G1)

• Checks whether the cell is big enough and has made the proper proteins for the synthesis phase

• If not, the cell goes through a resting period (G0) until it is ready to divide

(2) DNA synthesis checkpoint

• Occurs during the synthesis phase (S phase)

• Checks whether DNA hs been replicated correctly

• If so, the cell continues onto mitosis (M)

(3) Mitosis checkpoint

• Occurs during the mitosis phase (M)

• Checks whether mitosis is complete

• If so, the cell divides, and the cycle repeats

How to cancer treatments aim to reduce the rate of cell division?

By inhibiting some aspect of mitosis or the cell cycle in general. E.g. DNA replication or formation of the spindle during mitosis.