3.8.2.3 Gene expression and cancer

Question 1

What is a benign tumour

Answer 1

A benign tumour is non-cancerous does not invade surrounding tissues and does not spread to other parts of the body

Question 2

What is a malignant tumour

Answer 2

A malignant tumour is cancerous invades surrounding tissues and spreads to other parts of the body via the blood or lymphatic system

Question 3

What is the role of tumour suppressor genes in the development of tumours

Answer 3

Tumour suppressor genes normally slow cell division repair DNA or trigger apoptosis If mutated they become inactive leading to uncontrolled cell division and tumour formation

Question 4

What is the role of oncogenes in the development of tumours

Answer 4

Oncogenes are mutated proto-oncogenes that stimulate uncontrolled cell division leading to tumour formation

Question 5

How does abnormal methylation of tumour suppressor genes lead to cancer

Answer 5

Hypermethylation of tumour suppressor genes prevents transcription of the gene leading to loss of tumour suppressor protein function and uncontrolled cell division

Question 6

How does abnormal methylation of oncogenes lead to cancer

Answer 6

Hypomethylation of oncogenes leads to their overexpression causing increased stimulation of cell division and tumour formation

Question 7

How can increased oestrogen concentrations contribute to the development of some breast cancers

Answer 7

Oestrogen binds to oestrogen receptors in breast cells stimulating cell division increasing the risk of mutations and uncontrolled cell division

Question 8

How could oncogene knowledge be used in cancer treatment

Answer 8

Drugs can be designed to block overactive oncogene proteins or their receptors to slow down cell division

Question 9

How could tumour suppressor gene knowledge be used in cancer treatment

Answer 9

Gene therapy could introduce functional tumour suppressor genes to restore normal control of cell division

Question 10

How could understanding methylation help in cancer prevention

Answer 10

Drugs targeting abnormal methylation patterns could restore normal gene expression preventing tumour formation

Question 11

How could understanding oestrogen’s role help in treating breast cancer

Answer 11

Hormone therapy such as tamoxifen blocks oestrogen receptors reducing stimulation of cell division in breast tissue

Question 12

Describe how alterations to tumour suppressor genes can lead to the
development of tumours.

Answer 12

1. (Increased) methylation (of tumour suppressor genes);

Accept abnormal methylation or hypermethylation
Ignore decreased acetylation of histones

2. Mutation (in tumour suppressor genes);
3. Tumour suppressor genes are not transcribed/expressed
   OR
   Amino acid sequence/primary structure altered;

Accept mRNA for transcription/transcribed
Accept tertiary structure altered
Accept different amino acid
Ignore reference to protein not being formed

4. (Results in) rapid/uncontrollable cell division;

Accept cell division cannot be regulated
Ignore growth

Question 13

Explain how increased methylation could lead to cancer.

Answer 13

1. Methyl groups (could be) added to (both copies of) a tumour
   suppressor gene;
2. The transcription of tumour suppressor genes is inhibited;
3. Leading to uncontrolled cell division.

Question 14

Give one way in which benign tumours differ from malignant tumours.

Answer 14

Cells of benign tumours cannot spread to other parts of the body /
metastasise;
OR
Cells of benign tumours cannot invade neighbouring tissues

Question 15

Explain how the methylation of tumour suppressor genes can lead to
cancer.

Answer 15

1. Methylation prevents transcription of gene;
2. Protein not produced that prevents cell division / causes cell
   death / apoptosis;
3. No control of mitosis.