85997
Description
Flashcards by reynoldslaura, updated more than 1 year ago
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Created by reynoldslaura
about 11 years ago
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| Question | Answer |
| in osteogenesis imperfecta (brittle bone disease) what faulty collagen process is affected? | Defect in genes for either the α1 or α2 strands of type 1 heterotrimeric collagen |
| What are the 4 main results of osteogenesis imperfecta mutations? (often missense point mutations resulting in substitution of glycine) | alter the amount of type 1 pro-collagen, alter the structure of the triple helical domain, alter residues of the COOH propeptide, alters the chain composition of type 1 procollagen due to decrease production of pro-α2 |
| Which would be more severe for O.I sufferers. A mutation in α1 or a mutation of the α2 stand of the type 1 collagen helix? | Mutation in α1 as there are 2 copies of it per helix |
| What are the three factors that determine the severity of OI? | 1. which gene is mutated (is it the gene for α1 or α2) 2. Which amino acid is substituted for glycine (is it sim. or diff. to glycine) 3. The position of the mutation (severest closer to COOH terminal- triple helix forms from that terminal) |
| What is gonadal mosaicism? | It is a mutation of a % of cells that go on to produce sperms or eggs. Parent is unaffected by the child may or may not inherit the faulty gene |
| Defect in what causes junctional epidermolysis bullosa? | Laminin - blistering in the dermal-epidermal junction |
| Defects in what cause dystrophic epidermolysis bullosa? | Defects in the gene encoding collagen type VII (a filamentous collagen formed of three identical chains- homotrimeric) the mutations can affect any codon and frequently cause premature termination- HOTSPOT exon 73 |
| What happens to collagen in scurvy? | Deficiency of vitamin C prevents hydroxylation of proline to hydroxyproline which results in defective pro-α chains. Stable triple helix cannot form due to INSUFFICIENT HYDROGEN BONDING! |
| What happens in chondrodysplasia? | Abnormalities in collage type II, IX, X and XI which affects ENDOCHONDRAL BONE FORMATION. This has a wide range of clinical severity- most important type is spondylo-epiphyseal dysplasia |
| What causes lathyrism? | Ingestion of β- aminopropionitrile which inhibits lysyl oxidase and prevents cross link formation and consequently a reduction hydroxylysine |
| What is osteoarthritis caused by? | Changes in collagen type IX with age- reduction in amount, loss of NC4 domain which gives alterations to surface properties of collagen fibrils |
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