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CANCER GENETICS Cause of cancer
-somatic mutations in critical growth controlling genes
-tumour suppressor genes- off switches
-oncogenes - on switches
-mismatch DNA repair genes- If DNA undergoes damage from sunlight, chemicals, cigarette smoke, the DNA repair genes rectify the damage. If DNA repair is not working mutations persist when cell reproduces.
-rare families have inherited (germline) mutations in some of those genes Oncogenes
-oncogenes are altered forms of the normal genes proto-oncogenes- these genes cause cells to grow and divide and are tightly controlled by other genes. Function :-the main role of proto-oncogenes is to code for proteins that allow for signal transduction pathway- complex multi-step pathway from the cell membrane, through the cytoplasm, to the nucleus
-Type of proto-oncogenes:
-Growth factors: these control transition of a cell from Go to cell cycle. Growth factors stimulate cells to grow by binding to growth factor receptors. E.g v-SIS oncogene
-growth factor receptors: some oncogenes encode for growth factor receptors with tyrosine kinase activity. These receptors span the membrane or are found in the cytoplasm. Mutations of this oncogene results in ligand independent activation
-intracellular transductor factors: E.g proteins with GTPase activity-when they bind to GTP they become active, intrinsic GTPase activity generate GDP-this inactivates the protein. Mutations in these genes result in increased GTPase activityunrestrained growth Mutation in the proto-oncogene- results in an ocogene that codes for a protein that is permanently active and results in the cell to keep on dividing. 1 mutation is sufficient for role in cancer development Tumour suppressor genes
-For tumour suppressor gene to cause cancer both copies need to be mutation
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