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23 Cards in this Set
- Front
- Back
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3 ways viral genetics are used in medicine?
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genetic modifications of viral genomes, non-genetic interactions at the level of viral protein, gene therapy using viral vectors.
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how can viral genomes be genetically modified?
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mutation during normal replication, evolution of virus, clinicla management eg emergence of drug resistance, recombination, and reassortment (bw two multi moleculed RNA genomed viruses)
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what clinical response can be produced if viral genetics are altered?
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increased virulence, altered antigenecity, antivira; drug resistance
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in the lab due a population of viruses usually have a homogenous or heterogeneous mixture of genomes? In nature?
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heterogeneous in both
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reasons for natural mutations in viruses?
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poor fidelity of pol, rapid rate of genome replication, RNA viruses do not have a proof reading mechanism.
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what are the conditionally leathal mutants?
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host range mutants (grow in one cell type but not another) and temp sensitive mutants
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example of attenuated mutant virus and vaccine use?
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poliovirus selected that could infect GI cells, no disease is caused bc they need to infect neurons, but you get immunity
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what are the mechanisms of recombination in DNA viruses? RNA viruses?
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physical breakage and rejoining of parental DNA molecules throught regions of sequence homology. Template switching during RNA replication, no physical breakage of RNA genomes
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describe marker rescue.
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if a virus has a mutation then if you add the WT gene that is a mutant in the virus, homologous recombination should occur
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describe copy choice recombination.
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two RNA plus strands with mutations in different spots, RNA pol can jump between the two so that it nullifies the mutations and you have wildtype template RNA note this is in nonsegmented viruses only
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describe reassortment.
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only in segmented RNA viruses. Co-infection of different strains makes progeny virions of mixed genomes
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how many NA's and HA's exist for type A flu?
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16 HA and 9 NA
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does antigenic drift cause change in subtype?
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no - it is a slow gradual change in the antigenic determinants (HA and NA)
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what is the vaccine potential in Flu with reassortment?
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get 2 molecules of RNA for the HA and NA and the 6 others from attenuated master virus, thus you get the Ab response without virus replication
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what are the mechanisms by which viral proteins of two viruses interact to allow formation of infectious virus?
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complementation (donate proteins for which the genes are mutated), pseudotyping (genome of one virus is put in the capsid of another), interference (block may be at several levels), and suppression (one mutation suppresses the effect of another mutation)
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can the virus produced by complementation replicate on their own?
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no the genome is still messed up
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define direct homologous interference.
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where two viruses use the same receptor and one virus is a stronger binder or in greater amount and it out competes the other virus
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define direct heterologous interference.
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during co infection, effects on the host cell by one virus results in inhibition of replication of the 2nd virus
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define interferon mediated heterologous interference.
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infected cells produce interferon which is released and causes neighboring cells to enter a protected anti viral state
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describe the defective interfering particles.
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smaller viral genes that have many deletions and need the wild type proteins form a WT virus to replicate, can alter the outcome if infection and can lead to persistenct infection as they temper the replication of the parent infectious virus.
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T/F suppression can be inter or intra genic.
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TRUE
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what is the goal of viral gene therapy and what are some ways it can help?
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goal is use viruses to inject DNA to cells specfically. In genetic disease, it would hopefully replace the gene, in aquired diseases lke cancer it would target defective cells and leave others unharmed
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what is the ideal virus vehicle for gene therapy?
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high concentrations, non pathogenic when transgene is inserted, fail to elicit neutralizing immune response, convenient production and reproducible, targets right cell type, transgene expression is efficient, integration is ideal goal for stable maintenance
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