Gene expression and cancer (A-level only)

Question 1

Benign tumours

Answer 1

Benign tumours are NOT cancerous.

Benign tumours consist of cells that are dividing uncontrollably but the cells cannot spread and invade other tissues.

Benign tumours can develop into malignant tumours.

Question 2

Malignant tumours

Answer 2

Malignant tumours are cancerous.

Malignant tumours consist of cells that are dividing uncontrollably and spread into other tissues and around the body.

Malignant tumours can be life-threatening and can grow rapidly.

Question 3

Tumour supressor genes

Answer 3

Tumour suppressor genes are genes found in all cells.

These genes inhibit cell division to regulate the rate at which cells divide.

Increased methylation of a tumour suppressor gene inhibits this gene.

When tumour suppressor genes are not expressed, cell division is not inhibited.

This causes the cells to divide uncontrollably.

Question 4

Oncogenes

Answer 4

Oncogenes are mutations in a gene called a proto-oncogene.

Oncogenes are capable of transforming a cell into a cancerous cell because they cause excessive cell division.

Proto-oncogenes normally stimulate cell division.

Decreased methylation of a proto-oncogene causes proto-oncogenes to be over-expressed.

Over-expression of proto-oncogenes stimulates cell division.

Question 5

Environmental factors that are associated with an increase in cancer include:

Answer 5

Exposure to radiation.
Smoking.
Alcohol consumption.
Eating a diet high in fat.

Question 6

Genetic factors that are associated with an increase in cancer include:

Answer 6

Having certain alleles.
E.g. The BRCA1 allele can increase the chance of developing breast cancer.

Question 7

Develop more sensitive tests:

Answer 7

More sensitive tests can be used to diagnose cancers.
E.g. Tests that screen specifically for the RAS mutation can detect bowel cancer early. RAS mutations are very common in bowel cancer.

Question 8

Develop drugs:

Answer 8

If we know what gene mutations cause cancer, drugs can be developed to target these specific gene mutations.

Treatment for cancer can be made more specific by differing the drugs according to the type of mutation.

E.g. Breast cancer caused by the HER2 mutation is treated specifically with Herceptin.

Question 9

Intensity of treatment:

Answer 9

The intensity of the treatment needed can be determined by identifying what mutation is the cause.

Some mutations are more aggressive and require a stronger treatment than others.