CGE: Cancer

Question 1

Acquired mutations

Answer 1

Mutations that occur in individual cells after fertilisation.

Question 2

What happens if mutations occur in genes that control the rate of cell division?

Answer 2

Lead to uncontrolled cell division.

Question 3

Tumour

Answer 3

A mass of abnormal cells.

Question 4

Cancers

Answer 4

Tumours that invade and destory surrounding tissue.

Question 5

What two types of genes control cell division?

Answer 5

• Tumour suppressant genes
• Proto-oncogenes

Question 6

What happens if a mutation occurs in tumour suppressor genes?

Answer 6

Inactivated - the protein that stop cells dividing or causes self-destruction isn’t produced. The cells divide uncontrollably.

Question 7

What happens when tumour suppressor genes are functioning normally?

Answer 7

Slow cell division by producing proteins that stop cells dividing or cause them to self-destruct (apoptosis).

Question 8

Oncogene

Answer 8

Mutated proto-oncogene.

Question 9

What do proto-oncogenes do when functioning normally?

Answer 9

Stimulate cell division by producing proteins that make cells divide.

Question 10

What happens if a mutation occurs in a proto-oncogene?

Answer 10

The gene becomes overactive, stimulating the cells to divide uncontrollably resulting in a tumour.

Question 11

What are the two different types of tumours?

Answer 11

Malignant and benign.

Question 12

Describe malignant tumours:

Answer 12

• Cancers
• Grow rapidly
• Invade and destory surrounding tissues.
• Can metastasise and spread to other parts of the body in bloodstream or lymphatic systems.

Question 13

Describe benign tumours:

Answer 13

• Not cancers
• Slower growing
• Often covered in fibrous tissue that stop cells invading other tissues.
• Often harmless - can cause blockages and put pressure on organs.
• Can become malignant.

Question 14

How are tumour cells different to normal cells?

Answer 14

• Irregular shape
• Nucleus is larger and darker - can have more than one
• Don’t produce all proteins needed to function
• Different antigens on their surface
• Don’t respond to growth regulating processes
• Divide more frequently than normal cells

Question 15

Methylation

Answer 15

Adding a methyl group

Question 16

Why is methylation of DNA important?

Answer 16

Regulate gene expressions - can control whether or not a gene is transcribed and translated.

Question 17

Hypermethylation

Answer 17

When methylation occurs too much.

Question 18

Hypomethylation

Answer 18

When methylation occurs too little.

Question 19

What happens when tumour supressor genes are hypermethylated?

Answer 19

• The genes are not transcribed.
• The proteins they produce to slow cell division aren’t made.
• Cells can divide uncontrollably by mitosis and tumours can develop.

Question 20

What happens when proto-oncogenes are hypomethylated?

Answer 20

• Act as oncogenes.
• Increase the production of proteins that encourage cell division.
• Stimulates cells to divide uncontrollably.
• Tumour forms.

Question 21

What is thought to increase a woman’s risk of developing breast cancer?

Answer 21

Increased exposure to oestrogen over an extended period of time.

• Can be result of starting menstruation earlier than usual or the menopause later than usual.*
• Or HRT.*

Question 22

What are the theories as to how oestrogen can contribute to the development of some breast cancers?

Answer 22

• Oestrogen stimulates certain breast cells to divide and replicate.
• Naturally increases risk of mutations occuring - increased chance of cancerous cells.
• Ability to stimulate division could mean that if cells become cancerous, rapid replication could be further assisted by oestrogen - tumours form quickly.
• Research suggest oestrogen can introduce mutations directly into DNA of breast cells - increases chances of cells becoming cancerous.