20.5 gene expression & cancer

Question 1

what is a malignant tumour?

Answer 1

cancerous

Question 2

what is a benign tumour?

Answer 2

non-cancerous

Question 3

what are oncogenes?

Answer 3

mutated form of proto-oncogenes / over-expression of proto-oncogene

Question 4

how do proto-oncogenes activate DNA replication?

Answer 4

1- stimulate cells to divide
2- cell division starts when growth factors attached to protein receptors on cell-surface membrane
-> genes are activated & leads to DNA replication

Question 5

what are the 3 roles of tumour suppressor genes?

Answer 5

1- slow down cell division
2- repair mistakes in dna
3- apoptosis - programmed cell death
-> prevent formation of tumours & maintain normal rate of cell division

Question 6

how does hypomethylation of proto-oncogenes increase chances of developing tumours?

Answer 6

leads to activation of oncogenes -> continued transcription & translation

Question 7

how does hypermethylation of tumour suppressor genes increase chances of developing tumours?

Answer 7

occurs in promotor region -> TSG is not transcribed & switched off

Question 8

which tumour suppressor gene is the cause for most cancers? what does its mutations lead to?

Answer 8

TP53 - controls apoptosis
mutation leads to continued cell division & formation of tumours

Question 9

why are women more likely to develop breast cancer after menopause?

Answer 9

increased oestrogen production in fat cells in the breast

Question 10

how is the development of tumour in the breast form a positive feedback loop?

Answer 10

1- tumour increases oestrogen production & promotes growth of tumour
2- white blood cells drawn towards tumours also increases oestrogen formation

Question 11

how does oestrogen cause a proto-oncogene to turn into a oncogene?

Answer 11

oestrogen binds to a transcription factor & activates a gene