Gene Expression and Cancer Flashcards
Cancer is caused by [1] mitosis and this can lead to a abnormal mass of cells known as a [2].
[1] uncontrolled
[2] tumour
Benign tumour characteristics
slow growing;
surrounded by a capsule;
do NOT metastasise;
Malignant tumour characteristics
fast growing;
non-capsulated;
metastasise;
(spread to other parts of body)
The rate of tumour development is controlled by which genes?
Tumour suppressor genes
Oncogenes
Role of tumour suppressor genes
Slow down / regulate the rate of cell cycle
Role of proto-oncogenes
Speed up the rate of the cell cycle
Role of oncogenes
Speed up the rate of cell cycle;
Leads to uncontrolled cell cycle / mitosis;
How do oncogenes arise?
Random mutations in proto-oncogenes
BRCA1 and BRCA2 are human genes that code for tumour suppressor proteins.
Mutations in BRCA1 and BRCA2 can cause cancer. Explain how (3 marks).
- Change in DNA base sequence;
- Change in primary structure / sequence of amino acids
OR Change in tertiary structure
- Results in rapid / uncontrollable cell division / mitosis;
Increasing methylation of which gene could lead to the development of a tumour?
Tumour suppressor genes
As increasing methylation decreases transcription
Increasing acetylation of histones near which gene could lead to the development of a tumour?
Oncogenes
Treatment with drugs might be able to reverse the epigenetic changes that cause cancers.
Suggest and explain how (3 marks).
- Increase methylation of oncogene(s);
- Increasing methylation inhibits / decreases transcription;
- Decrease methylation of tumour suppressor gene;
- Decreasing methylation stimulates / increases transcription;
- Increase acetylation of histones stimulates transcription / gene expression;
(e.g. of tumour suppressor gene)
Myelodysplastic syndromes (MDS) are a group of malignant cancers of blood cells.
MDS can develop from epigenetic changes to tumour suppressor genes. In some patients, the drug AZA has reduced the effects of MDS. AZA is an inhibitor of DNA methyltransferases. These enzymes add methyl groups to cytosine bases.
Suggest and explain how AZA can reduce the effects of MDS in some patients (3 marks).
- AZA reduces methylation of DNA/cytosine;
- Tumour suppressor gene is transcribed/expressed;
Accept mRNA produced for transcription/transcribed.
- Prevents rapid/uncontrollable mitosis
OR cell division can be controlled/stopped/slowed;
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.
Suggest how EGCG allows the production of mRNA in daughter cells (3 marks).
- EGCG binds to active site of DNMT;
- DNMT cannot methylate / less methylation of promoter region of tumour suppressor gene;
- Transcription factor(s) can bind to promoter region;
- RNA polymerase stimulated;
increased concentration of which hormome are linked to the development of some breast cancers?
Oestrogen
ER-positive breast cancers have receptors for the hormone oestrogen. These cancers develop as a result of increased oestrogen concentrations in the blood. Effective treatment of ER-positive breast cancers often involves the use of drugs which have a similar structure to oestrogen.
Suggest and explain how these drugs are an effective treatment of ER-positive breast cancers (3 marks).
- Drug binds to oestrogen/ER receptor;
- Prevents binding of oestrogen
- No/fewer transcription factor(s) bind to promoter
OR RNA polymerase not stimulated
