cancer exam questions

Question 1

Increased methylation of the promoter region of a tumour suppressor gene
causes one type of human throat cancer.
In this type of throat cancer, cancer cells are able to pass on the increased
methylation to daughter cells. The methylation is caused by an enzyme called
DNMT.
Scientists have found that a chemical in green tea, called EGCG, is a
competitive inhibitor of DNMT. EGCG enables daughter cells to produce
messenger RNA (mRNA) from the tumour suppressor gene.
(b)
Suggest how EGCG allows the production of mRNA in daughter cells (3)

Answer 1

EGCG binds to active site of DNMT
DNMT cannot methylate
transcription factors can bind
RNA polymerase activated.

Question 2

The scientists investigated the effect of different amounts of EGCG on the
growth rate of the throat cancer cells grown in vitro. Their results are shown in
the graph below.
(c)
A reporter who reviewed all of this work concluded that drinking green tea
could be a cure for cancer.
Suggest three reasons why his conclusion might not be valid. (3)

Answer 2

may only work for throat cancer

do not know how much EGCG is in green tea

only significant for 20 and 50 level

Question 3

Describe how alterations to tumour suppressor genes can lead to the
development of tumours. (3)

Answer 3

mutation
hypermethylation of tumour suppresor gene

gene not transcribed
uncontrollable cell division

Question 4

A type of malignant tumour cell divides every 8 hours.
Starting with one of these cells, how many tumour cells will be present after
4 weeks?
Assume none of these cells will die.
Give your answer in standard form.
Answer = ____________________
(2)
(Total 6 marks)
Sometimes, a mutagenic agent causes DNA to break. A different enzyme
called ATM binds to the broken DNA. This leads to the activation of a
protein coded for by a tumour suppressor gene. The effect of ATM binding
is to stop cell division until DNA is repaired.
A mutation could result in a person having non-functional forms of the gene
that produces ATM.
What can you predict about the possible effects of having a non-functional
form of ATM? (3)

Answer 4

ATM doesn’t bind to DNA
DNA not repaired
cell division continues

Question 5

Explain how increased methylation could lead to cancer. (3)

Answer 5

Methyl groups (could be) added to (both copies of) a tumour
suppressor gene;
2.
3.
The transcription of tumour suppressor genes is inhibited;
Leading to uncontrolled cell division.

Question 6

Give one way in which benign tumours differ from malignant tumours (1)

Answer 6

benign tumours cannot spread to other parts of the body/metastise

Question 7

Give one way in which benign tumours differ from malignant tumours.

Explain how the methylation of tumour suppressor genes can lead to
cancer.

Answer 7

methylation prevents transcription of gene
protein that reduces cell division not produce
no control of mitosis.

Question 8

Treatment with isoniazid leads to the osmotic lysis of this bacterium. Use information in
thediagram to suggest how. (2)

Answer 8

-bacteria has lower water potential
-water enters via osmosis and causes lysis/bursting.

Question 9

(b)
Describe how altered DNA may lead to cancer. (6)

Answer 9

-mutation changes DNA base sequence of
-tumour suppressor gene
-oncogene
-protein not formed
-tumour suppressor gene produces protein that reduces cell division
-uncontrollable cell division
-malignant tumour

Question 10

Explain why fragments of DNA from cancer cells may be present in blood plasma (2)

Answer 10

-cancer cells break open/releasing DNA