Tumors and Mutations

Question 1

What are the characteristics of benign tumours?

Answer 1

• They have a capsule around them called a basement
membrane
• They do not invade neighbouring tissues
• They do not spread to other parts of the body

Question 2

What are the characteristics of malignant tumours?

Answer 2

• They invade the basement membrane and no ;longer
have a capsule
• They can survive in low oxygen environments
so can grow deep within tissues and in places
where blood supply is limited
• They invade other body tissues causing damage
to multiple different tissues
• They can spread and cause secondary tumours
in other parts of the body
• They are harder to detect, remove and treat

Question 3

What are proto-oncogenes

Answer 3

proto-oncogenes code for proteins that stimulate cell
division (e.g. in response to growth hormone)

Question 4

what are tumour suppressor genes

Answer 4

tumour suppressor genes code for proteins that slow/stop
cell division or cause cell death. (e.g. in response to damaged
DNA).

Question 5

How do mutations in DNA lead to tumour formation?

Answer 5

Proto-oncogenes can mutate to form oncogenes.
• The oncogenes can cause cells to keep dividing at a fast
rate
• Mutated tumour suppressor genes increases cell
division and does not promote cell death.
• Both mutations result in an abnormal cell cycle and
results in cells dividing uncontrollably causing a tumour
to develop.