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Stack #4624459
| Question | Answer |
|---|---|
| Define inherited diseases: | —> mutations in genes encoding for essential functional proteins |
| Cancer | —> mutations in genes encoding for proteins involved in the regulation of growth + survival |
| What are polymorphisms? | —> Different gene sequences which can cause altered phenotype function but not necessarily disease |
| What are alleles? | —> genes encoding different polymorphic forms of proteins |
| Heterozygosity | —> two copies of genes to minimise loss of function due to mutations |
| Apoptosis | —> damaged cells killed to prevent transmission of mutation genes |
| Define the cell cycle control | —> checkpoints during cell division to ensure cell is healthy, no damaged DNA |
| What is regulation of gene transcription required for? | Appropriate activation signals to induce gene expression |
| What are the 3 classes of factors that cause mutations? | 1) ENVIRNOMENTAL 2) INHERITED 3) VIRAL |
| List some environmental factors | - chemical = cigarette smoke, mouldy peanuts - radiation = Chernobyl, UV exposure |
| List some inherited factors | Mutations in germ-line DNA |
| List some viral factors | Rous sarcoma virus + HPV (cervical cancer) |
| How can sequence mutations change ‘normal’ genes into ‘aberrant’ genes? | 1) DELETIONS or INSERTIONS might scramble the encoded mRNA —> complete loss of functional protein 2) SINGLE BASE MUTATION lead to singe amino acid difference in altered protein leading to a change in functional activity + - |
| Name 3 monogenic diseases | 1) CYSTIC FIBROSIS 2) SICKLE CELL ANAEMIA 3) X-SCID |
| What is cystic fibrosis? | F508-CFTR - 3 nucleotide deletion loss of phenylalanine —> incorrect folding + subsequent degradation |
| What is sickle cell anaemia? | A to T of the beta globin gene - glutamic acid substituted by valine |
| What is X-SCID? | Mutation in cytokine receptor signalling chain = immunodeficiency |
| What are oncogenes? | —> mutated forms of normal cellular genes (proto-oncogenes) which control cell growth |
| Why do oncogenes only need mutation in one allele to increase function? | They are usually DOMINANT |
| What do oncogenes encode for? | - Growth factors - receptors - signal transducers - nuclear transcription factors e.g. Ras, c-myc |
| A point mutation in Ras causes what? | It becomes constitutively active, no longer requires signals from receptor - activates Ras-MAPK signalling pathway - increased gene transcription |
| What is EGF? | Important growth factor - drives CELL PROLIFERATION |
| Intrinsic kinase domain leads to activation ? | Activation downstream signalling pathways - Ras/MAPK + P13K-PKB |
| Mutations in receptor can cause what? | - ligand independence - constitutive dimerisation - over expression - gene amplification |
| Amplification of WT rec can cause what cancer? | HER2 + breast cancer |
| Mutations that inactivate tumour suppressor genes promote wheat? | Aberrant cell growth! - usually autosomal RECESSIVE - require loss of both alleles |
| Give an example of inherited mutation | Li Fraumeni syndrome = inherited mutation in p53 = many childhood tumours |
| What are TRANSLOCATIONS? | —> aberrant cross-overs between chromosomes during cell division |
| What can translocations lead to? | Lead to genes normally regulated by one promoter becoming separated from this and NOW controlled by another - this can dysregulate gene expression + lead to alterations in cell growth, susceptibility to death |
| What is bcl-2? | = anti-apoptotic protein = B cell lymphoma = translocated to come under control of the Ig promoter |
| Bcl-2 over expressed causes? | Reduced ability to die by apoptosis = tumour growth |
| Lung cancer mutations are commonly caused by ewhat? | Environmental carcinogens e.g. cigarette smoke. |
| 60% human lung cancers have mutations in what gene? | P53 |
| What compound in cigarette smoke is metabolised in liver generating a potent mutagen? | Benzo(a)pyrine - mutagen causes G>T transversions in DNA = hot spots in p53 in DNA binding region |
| Give some regimes for targeting lung cancer | - chemotherapy (cytotoxic drugs) - radiotherapy - restoring p53 function in development - targeted therapies (EGFR inhibitors) - Iressa (gefitinib) - only active in hypermutatedd EGFR - Tarceva (erlotinib) - Afatinib |
| For radioctherapy and chemotherapy what is the potential issue for treatment of some cancers? | Issue potentially for cancers that are p53 deficient! |
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Study109