Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
24 Cards in this Set
- Front
- Back
|
What are the characteristics of the viral nucleic acid core? |
DNA or RNA Single or Double stranded segmented or non segmented |
|
|
Difference between capsid and nucleocapsid? |
capsid= protein coat surrounding nucleic acid; made up of capsomeres
nucleocapsid= nucleic acid associated with viral capsid proteins |
|
|
Icosahedral nucleocapsid? |
protein subunits arranged in 20 identical equilateral triangles, has 30 edges and 12 vertices
have two, three, and five fold axis of symmetry
thermodynamically stable |
|
|
helical nucleocapsid? |
having cylindrical shape, capsomeres bind viral genome in periodic fashion |
|
|
Complex capsid? |
do not exhibit icosahedral or helical symmetry |
|
|
Difference between enveloped and non-enveloped viruses? |
enveloped- viruses bud through a cell membrane acquiring lipoprotein coat. Contain virally encoded glycoproteins. Sugars added by host cell.
-matrix proteins= mediate interactions between the capsid and envelope
-other proteins such as viral polymerases, phosphatases, ligases, and kinases may be included within envelope |
|
|
Site of replication in DNA viruses? |
most multiple in the nucleus of infected cells and have double stranded genomes and icosahedral capsids
-some can still have singles stands, and some can still replicate in the cytoplasm |
|
|
Site of replication for RNA viruses? |
replicate in the cytoplasm of infected cells and have single stranded RNA and envelopes.
-some, like reoviruses, have double stranded RNA -some, like hep D, replicate in the nucleus |
|
|
What are the basic steps in Viral Replication (both DNA and RNA)? |
Attachment- involves cellular receptors Penetration- endocytosis or fusion Uncoating- involves cellular or viral enzymes Macromolecular synthesis- protein and nucleic acids Assembly Release
|
|
|
Macromolecular synthesis for DNA viruses? |
-replication in nucleus (except poxvirus) -synthesis of early mRNA using cellular polymerase -synthesis of early proteins in cytoplasm (may include DNA polymerases, transported back to nucleus) -DNA replication, usually semiconservative, but replicative intermediates differ -synthesis of late mRNA -syntheis of late (structural proteins) |
|
|
Macromolecular synthesis for single stranded (+) RNA viruses |
-dont require a virion associated polymerase, but the genome must encode a polymerase -viral RNA serves as a template for synthesis of complementary strands, which in turn serve as templates for synthesis of new viral RNA -no clear distinction between early and late steps
|
|
|
Macromolecular synthesis for single stranded (-) RNA viruses |
-RNA cannot serve as messenger; must have virion associated RNA polymerase to transcribe RNA, genome must also encode said polymerase -viral RNA serves as template for complementary strand, which in turn serve as templates -no clear distinction between early and late steps |
|
|
What is the most common method for growing viruses? |
cell culture- tissue must be dissociated into single cell suspension and put into a vessel that has appropriate growth surface
must be supplemented with serum as a source of growth factors and other factors |
|
|
Difference between primary cell culture and cell strains? |
cell strains are subcultures of a primary culture; these retain their diploid chromosome number but usually have a limited lifespan.
may acquire different properties than primary culture |
|
|
Difference between Cell lines and Cell strains? |
Cell lines are immortalized (like Matt in the history of pop-punk bassists) and can propagate indefinitely.
usually do not retain their diploid chromosome number |
|
|
What is cytopathic effect? |
change in appearance in cell culture, i.e. syncytia, inclusion bodies |
|
|
Why is PCR helpful in detecting viruses? |
can be used to detect specific viral nucleic acid |
|
|
What are plaques forming in cell culture useful for? |
to quantify how many infectious viral particles may be present |
|
|
Why do RNA viruses have a higher rate of spontaneous mutations than DNA viruses? |
DNA= one error per 10^8-10^11 RNA= error per 10^3=10^5
RNA dependent RNA polymerases and reverse transcriptases do not have proof-reading capacity |
|
|
What is a replication defective virus and how can it replicate within a host? |
require a "helper" virus to replicate. They may occur naturally or be induced.
Hep D virus is an example, needs Hep B in order to replicate. Uses Hep B surface protein. |
|
|
What is the process of recombination between two viruses? |
exchange of nucleic acid sequences between genomes of viruses in the same cell.
-progeny have different phenotypic and genotypic properties from either parent -coinfection of a cell with two mutants of the same virus may result in a wild type progeny as a result of recombination |
|
|
Process of reassortment? |
viruses containing segmented genomes
two strains or mutants of a virus in a cell can result in progeny that have packaged nucleic acid segments derived from both parents
-progeny have different phenotypic and genotypic properties from either parent -coinfection of a cell with two mutants of the same virus may result in a wild type progeny as a result of reassortment |
|
|
What is complementation and how does it effect replication deficient viruses? |
the ability of one virus to provide a functional gene product for another in which the gene is mutated or missing
-no exchange of genetic material -results in progeny identical to their parents - coninfection of a cell with two mutants will not yield wild type progeny as a result of complementation |
|
|
Macromolecular synthesis in Hepadnaviruses (Hep B)? |
-DNA copied to RNA -RNA recopied to DNA by reverse transcriptase -analogous to retroviruses, except viral genome is DNA |
