8.2.3 Gene expression and cancer

Question 1

What is cancer?

Answer 1

Cancer is a group of diseases caused by damage to the genes that regulate mitosis and the cell cycle.

Question 2

What are malignant tumours?

Answer 2

Malignant tumours are cancerous tumours.

Question 3

What are benign tumours?

Answer 3

Benign tumours are non-cancerous tumours.

Question 4

What are the characteristics of benign tumours?

Answer 4

Benign tumours have slow growth, defined boundaries, retain function and normal shape, do not spread easily, and are easy to treat.

Question 5

What are the characteristics of malignant tumours?

Answer 5

Malignant tumours have rapid, uncontrollable growth, undefined boundaries, cells that do not retain function, spread quickly, and are difficult to treat.

Question 6

From what are cancer cells derived?

Answer 6

Cancer cells are derived from a single mutant cell.

Question 7

What does a single mutant cell cause?

Answer 7

It causes uncontrolled cell division and uncontrolled mitosis in the cell.

Question 8

What are the two main types of genes that play a role in cancer?

Answer 8

Tumour suppressor genes and oncogenes.

Question 9

What are oncogenes?

Answer 9

Oncogenes are mutations of proto-oncogenes.

Question 10

What do proto-oncogenes do?

Answer 10

stimulate a cell to divide when growth factor attach to protein receptor on cell surface membrane

activates genes that cause DNA to replicate

cell divides

can become permanently activated (switched on)

Question 11

What happens if a proto-oncogene mutates to an oncogene?

Answer 11

It can become permanently activated (switched on).

Question 12

Why can oncogenes become permanently activated?

Answer 12

1 - Receptor protein on cell surface membrane can be permanently activated, causing cell division even in the absence of growth factors. 2 - Oncogene may code for a growth factor produced in excessive amounts, leading to excessive cell division.

cell division too rapid and out of control - tumour

Question 13

What do oncogenes lead to?

Answer 13

Oncogenes lead to cell division being too rapid and out of control, resulting in tumours.

Question 14

How can some cancers be caused?

Answer 14

By inherited mutations of proto-oncogenes

cause the oncogens to be activated

Question 15

tumour suppressor genes

Answer 15

Tumour suppressor genes slow down cell division, repair mistakes in DNA, and tell cells when to die (apoptosis)- (programmed cell death)

Question 16

what do tumour supressor genes do

Answer 16

maintain a normal rate of cell division
prevent formation of tumours

Question 17

What happens if a tumour suppressor gene becomes mutated?

Answer 17

It becomes inactive (switched off).

Question 18

What happens if a tumour suppressor gene becomes inactive?

Answer 18

It stops inhibiting cell division, causing cells to grow out of control.

Question 19

How does the inactivation of tumour suppressor genes cause tumours?

Answer 19

Mutated cells can clone themselves, making tumours.

Question 20

What is the difference between oncogenes and tumour suppressor genes?

Answer 20

Oncogenes cause cancer as a result of the activation of proto-oncogenes, while tumour suppressor genes cause cancer when inactivated.

Question 21

What is abnormal DNA methylation?

Answer 21

common in developing tumours and involves increased methylation.

Question 22

What is hypermethylation?

Answer 22

increased methylation.

Question 23

Describe the process of hypermethylation leading to cancer.

Answer 23

• occurs in specific region (promoter region) of tumour supressor genes
• Becomes inactivated
• transcription of promoter region of TSG inhibited
• TSG switched off
• Increased cell division
• forms tumours

Question 24

Reduced methylation

Answer 24

hypomethlylation- in oncogenes - forms tumours

Question 25

What is hypomethylation?

Answer 25

Hypomethylation refers to reduced methylation in oncogenes, which can form tumours.

Question 26

What causes an increase in breast cancer?

Answer 26

An increase in oestrogen concentration.

Question 27

How can oestrogen cause tumour development?

Answer 27

Oestrogen activates a gene that promotes transcription. If this gene controls cell division and growth, it will be continuously activated, leading to uncontrolled cell division and tumour formation. Oestrogen can also cause proto-oncogenes in breast tissue to become oncogenes, leading to breast cancer

Question 28

What is the link between oestrogen and breast cancer?

Answer 28

High concentrations of oestrogen in adipose tissue can over-activate cell division, leading to uncontrolled growth.

Question 29

How does a benign tumour differ from a malignant tumour (1)

Answer 29

Benign tumours do not invade tissues or spread (metastasize).

Question 30

How can tumours harm the body? (2)

Answer 30

Tumours can damage organs and cause blockages or pressure on organs.

Question 31

Explain the link between sunbathing and skin cancer.

Answer 31

UV radiation causes mutations in genes controlling cell division.

Question 32

Why are fair-skinned people more at risk for skin cancer?

Answer 32

They have less melanin, providing less protection from UV.

Question 33

Why does a family history increase cancer risk? (1)

Answer 33

There may be an inheritance of oncogenes or predisposition genes.

Question 34

How can a tumour suppressor gene mutation cause tumours? (1)

Answer 34

The gene becomes inactivated, leading to uncontrolled cell division.

Question 35

Why do some mutations not change the amino acid sequence? (1)

Answer 35

The genetic code is degenerate; mutations may occur in non-coding DNA.

Question 36

How do monoclonal antibodies stop tumour growth? (3)

Answer 36

The antibody binds to the receptor, preventing growth factor binding and stopping cell division stimulation.

Question 37

How does methylation of tumour suppressor genes lead to cancer? (3)

Answer 37

It prevents transcription, resulting in no protein to prevent division and uncontrolled mitosis.

Question 38

Define epigenetics. (2)

Answer 38

heritable gene function changes without changes in the DNA sequence.

Question 39

Which control factors bind DNA/protein?

Answer 39

Oestrogen binds protein; Methyl binds DNA; Acetyl binds protein.

Question 40

How does increased methylation lead to cancer? (3)

Answer 40

Increased methylation silences tumour suppressor genes, preventing transcription and leading to uncontrolled cell division.

Question 41

How do benign and malignant tumours differ? (1)

Answer 41

Benign tumours do not metastasize or invade other tissues.

Question 42

How do tumour suppressor gene alterations lead to tumours? (2)

Answer 42

Methylation or mutation prevents gene transcription, leading to no control of mitosis and uncontrolled division.

Question 43

How does an activated oestrogen receptor affect target cells? (2)

Answer 43

It binds to DNA and promotes transcription.

Question 44

Why does oestrogen only affect target cells? (1)

Answer 44

Only target cells have complementary receptors.

Question 45

How does endoxifen reduce breast tumour growth? (2)

Answer 45

Competes with oestrogen; Blocks receptor activation.

Question 46

Why does an antibody bind to a transcription factor? (2)

Answer 46

The antibody has a complementary shape, forming an antigen-antibody complex.

Question 47

What is a genome? (1)

Answer 47

complete set of an organism's DNA.

Question 48

What is a malignant tumour? (3)

Answer 48

A malignant tumour invades tissues, metastasizes, and causes damage.

Question 49

Why does the death rate from malignant skin tumours increase with age?

Answer 49

There is longer UV exposure leading to more mutations.

Question 50

Why does skin colour affect skin cancer death rate? (2)

Answer 50

Darker skin has more melanin, providing more UV protection.