13074966
Description
Flashcards by Raheem Chaudhry, updated more than 1 year ago
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Created by Raheem Chaudhry
about 6 years ago
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| Question | Answer |
| Describe the different types of genetic mutations. [6 marks] | Insertions, Deletions, Substitutions. Substitutions can be 'missense' or 'nonsense' mutations. Insertions and deletions can be frameshift mutations. Plus: Splice shifts (intron/exon site lost). |
| Describe nonsense-mediated mRNA decay. [2] | Cellular mechanisms detect that mRNA is improper (due to nonsense or splice shift) and degenerate mRNA before protein product can be formed. |
| Briefly outline the Gene-to-Protein pathway. [3] | Gene --Transcription--> Primary mRNA --splicing--> Mature mRNA --Translation--> Protein |
| Effects of different types of mutations. [4] | Loss-of-function Gain-of-function Dominant-negative (loss-of-function) Gene-dosage affecting |
| Define "Loss-of-Function" mutations and give a pathological example. [2] | Where the gene product has reduced or none of normal function e.g. Duchenne Muscular Dystrophy (DMD). |
| What is the role of dystrophin? [2] | It links the cell with the matrix of the myofilament. Found in the sacrolemma. |
| What sort of mutation is most likely to cause Duchenne Muscular Dystrophy? [1] | Frameshift mutation |
| Inheritance of Duchenne Muscular Dystrophy. [1] | X-linked recessive |
| What is Gower's Sign? [1] | Where the patient has to use their hands and arms to "walk" up their body from a squatting position due to lack of hip and thigh muscle strength. |
| Describe "Gain-of-Function" mutations. [2] | Where the gene product acquires a new, abnormal function. However, only the specific mutation that gives the product its new function will result in the clinical phenotype. |
| Give an example of a "gain-of-function" mutation resulting in a pathological condition. [2] | HTT gene mutation results in Huntington's Disease. |
| Describe the specific mutation in Huntington's Disease and its affect. [6] | Expanded and unstable CAG repeats in exon 1 of the HTT (huntingtin) gene. A normal allele will have 9-35 CAG repeats but an affected allele will have 36-100 CAG repeats. This results in a polyglutamine tract in the protein causing the protein to aggregate + cause neuronal death. |
| Define "dominant-negative" mutations. [2] | A mutation where the mutant gene product not only loses its own function but also prevents other gene products from functioning correctly. |
| Explain how Osteogenesis Imperfecta is an example of the dominant-negative effect. | It is a mutation in Type I collagen. It has mild and lethal phenotypes depending on whether the mutated alpha chain is incorporated into the collagen. The alpha chain mutation affects bone and collagenous structures. |
| What is the "gene dosage effect"? Give an example of the effect in pathology. | Where the mutation varies the level of gene product. An example is Down's Syndrome (additional Chromosome 21). |
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