Cancer

Question 1

What is cancer the result of?

Answer 1

Mutations in the genes that regulate mitosis

Question 2

If mitosis is not regulated, what does this lead to?

Answer 2

uncontrollable cell division/ growth thus creating a tumour

Question 3

What is a benign tumour?

Answer 3

non-cancerous

Question 4

What is a malignant tumour?

Answer 4

cancerous

Question 5

What makes a benign tumour non-cancerous?

Answer 5

Adhesion molecules produced so they stick and to a particular tissue –> do not move
Capsule - remain compact, do not spread and can often be removed by surgery –> rarely return
So the impact of the tumour is localised and is often not life-threatening.

Question 6

Explain the growth of a benign tumour?

Answer 6

They can grow large but they grow at a very slow rate.

Question 7

What are the properties of malignant tumours?

Answer 7

They are cancerous
Grow large rapidly
The cell nucleus becomes large and the cells can become unspecialised again
They do not produce adhesive, so the tumour can metastasise which means that the tumour can break off and spread to other parts of the body
Not contained within a capsule/membrane
So they can grow projections into surrounding tissues and develop its own blood supply
Can be lifethreatening and removal requires surgery and supplementary treatment e.g. radio/chemotherapy
Recurrence is more likely

Question 8

What are oncogenes?

Answer 8

The mutated version of a proto-oncogene. Proto-oncogenes create a protein which initiates DNA replication during interphase of the cell cycle so that mitosis can occur when the body needs to make new cells, however the mutation of proto-oncogenes can result in this process being permanently activated so cells continually divide.

Question 9

What two genes control mitosis?

Answer 9

Proto-oncogenes
Tumour suppressor genes

Question 10

What do tumour suppressor genes do? (TSG)

Answer 10

They produce a protein which slows down cell division and causes cell death (apoptosis) if DNA copying errors are detected.

Question 11

What happens if aTSG becomes mutated?

Answer 11

Mutation leads to the transcription of the TSG becoming inhibited so the TSG will not produce the protein which slows down cell division - so it continues and mutated cells would not be identified and destroyed so leads to uncontrolled cell division.

Question 12

Describe how abnormal methylation leads to the TSG to be turned off?

Answer 12

Hypermethylation - increased number of methyl groups are added to the TSG resulting in the gene becoming inactivated and turned OFF.

Question 13

Describe how abnormal methylation leads to proto-oncogenes being turned off?

Answer 13

Hypomethylation occurs - a reduced number of methyl groups are added to the oncogenes which results in the gene being permamnently switched ON. So lots of proteins being made which initiate the cell cycle

Question 14

Why is oestrogen produced and what produces it?

Answer 14

Produced by the ovaries to regulate the menstrual cycle but stops getting produced after the menopause

Question 15

After the menopause, what produces oestrogen?

Answer 15

Fat cells in the breast tissue - this has been linked with causing breast cancer in women post-menopause

Question 16

How does oestrogen lead to breast cancer?

Answer 16

It can interfere with the transcription of the genes involved in the cell cycle.

Question 17

Give 6 properties of tumour cells:

Answer 17

Nucleus is darker + larger than normal, some cells have more than one
Have an irregular shape
Don’t produce all of the proteins needed to function properly
They have different antigens on their surface
Do not respond to growth regulating processes
They divide by mitosis more frequently than normal cells

Question 18

What increases a woman’s chances of getting breast cancer?

Answer 18

Increased exposure to oestrogen over an extended period of time

Question 19

What are the theories as to why oestrogen increases the chances of breast cancer?
Give one (1)

Answer 19

Oestrogen can stimulate certain breast cells to divide and replicate. The fact that more cell divisions are taking place naturally increases the chances of mutations occuring and so increases the chances of cells becoming cancerous

Question 20

What are the theories as to why oestrogen increases the chances of breast cancer?
Give one (2)

Answer 20

If cells do become cancerous, then oestrogens ability to stimulate division = rapid replication could be further assisted by oestrogen, helping tumours form quicky.

Question 21

What are the theories as to why oestrogen increases the chances of breast cancer?
Give one (3)