F. Yr 13 cancer Flashcards
(33 cards)
What is a malignant tumour
A cancerous tumour
What is a benign tumour
A non-cancerous tumour
Name some characteristics of benign tumours
- can grow to large size
- grow slowly
- must less likely to be life threatening but can disrupt organ function
- have localised effect on the body
- cells are often well differentiated
Name some characteristics of malignant tumours
- can grow to large size
- grow rapidly
- more likely to be life threatening as abnormal tissue replaces normal
- have a systemic (whole body) effect such as weight loss and fatigue
- cells become de-differentiated
What happens during the development of cancer
- cancer cells are derived from a single mutant cell
- the initial mutation causes uncontrolled mitosis
- later a further mutation in one of the descendant cells leads to other changes that cause subsequent cells to be different from normal in growth and appearance
Name the two main types of genes that play a role in cancer
- tumour suppressor genes
- oncogenes
What are proto-oncogenes
- genes that stimulate a cell to divide
- when growth factors attach to a complementary protein receptor on its cell surface membrane
- this activates the genes causing DNA to replicate and the cell to divide
How do proto-oncogenes cause the cell to divide
- when growth factors attach to a complementary protein receptor on its cell surface membrane
- it activates the genes causing DNA to replicate and the cell to divide
What happens when a proto-oncogene mutates into an oncogene
It becomes permanently switched on
Why does a proto-oncogene become permanently switched on
- the receptor protein on the cell-surface membrane can be permanently activated so that cell division is switched on even in the absence of growth factors
- the oncogene may code for a growth factor that is then produced in excessive amounts again, stimulating excessive cell division
Name two ways cancer can occur
- mutation of proto-oncogenes
- mutation of tumour suppressor genes
What do tumour suppressor genes do
- slow down cell division
- repair mistakes in DNA
- and ‘tell’ cells when to die (undergo apoptosis)
What is apoptosis
Cell programmed death
How do tumour suppressor genes prevent the formation of tumours
They maintain normal rates of cell division
How can the mutation of tumour suppressor genes cause cancer
- mutation of tumour suppressor gene causes it to become inactive
- as a result it stops inhibiting cell division
- cells growth becomes out of control
- therefore cancer
How does the hypermethylation of tumour suppressor genes cause the formation of a tumour
- hypermethylation in a specific region of tumour suppressor genes (promotor region)
- this leads to inactivation of the gene
- transcription of the promotor regions of the tumour suppressor genes is inhibited
- inactivation means cell growth rate cannot be controlled
- leading to the formation of the tumour
What is hypermethylation
Increased methylation
Why does the hypermethylation of the on the tumour suppressor cause it to be inactivated
- preventing the binding of transcriptional factors to the gene
- attracting proteins that condense the DNA-histone complex (by inducing deacetylation of the histones) making the DNA inaccessible to transcription factors
What other type of abnormal methylation can occur that leads to tumours
- hypomethylation of oncogenes
- therefore activating these oncogenes
- therefore causing the formation of tumours
What happens during menopause
Increased production of oestrogen in fat cells of breasts
How does oestrogen cause a tumour to develop
- oestrogen activates a gene by binding to a transcription factor which stimulates transcription of a gene
- if oestrogen acts on a gene that controls cell division and growth it will be activated
What can oestrogen cause
Breast cancer
Define genome
The complete set of genes in a cell including those in mitochondria and or chloroplasts
What does WGS sequencing stand for
Whole genome shotgun sequencing
