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58 Cards in this Set
- Front
- Back
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Viral replication and expression - describe Genomic v anti-genomic
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1. quasi species "Fitness" - helps keep virus going
2. Recombination - small areas of x-over 3. Reassortment - pig is mixing vessel for influenza as takes in both human - bird . |
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Describe degrees of mutation in RNA viruses
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there is some degree of mutation in RNA viruses - polymerase has room for > errors. They don't go back in and double check for errors
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Describe splicing process
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in Mammalian genes, coding sequences (exons) are interrupted by non-coding sequences (introns). Introns have to be removed by RNA splicing to make true mRNA transcript.
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How are single stranded genomes described?
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kilobases - KB - thousands of bases.
Dbl stranded - KNP - KB pairs |
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Describe DNA virus characteristics (both ss and ds)
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1. many have circular genomes
2. replication in nucleus (x POXVIRUS) 3. Req early translation for req proteins for replication. - early and late protein mfg for replication. |
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Describe "Fitness" in relation to quasi species and sequencing.
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Is the seq taken directly from pt blood or from a culture? Blood has 'truer' seq, less room for mutation.
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Talk about DNA retrovirus
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dsDNA ~covalently closed circular (ccc) DNA ~ mRNA and pregenomic(pg) RNA ~ dsDNA
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Characteristics of DNA retroviruses
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1. genome is parially ds DNA
2. Similar strategy to RNA retroviruses |
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What are a few DNA viruses and specific characteristics
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Herpes and Poxviruses - lg DNA genomes >150 genes. No gene splicing and replicate in cytoplasm.
DNA hep B has a very unusual circular genome. Parvoviruses - small genome size of ssDNA. Lots of splicing to produce subgenomic mRNAs |
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What is typical dsDNA virus
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Adenoviruses.
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What protects the genome of a virus
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Coat or CAPSID which consists of CAPSOMERES.
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What are CAPSOMERES made up of?
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one - three polypeptides.
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What else can make up a virus besides the capsid?
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Lipid env.
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What is the nucleocapsid
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Nucleic acid core and capsid complexed together
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What is a virion
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complete virus particle.
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What are arrangements called in most nucleocapsids
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helical or icosahedra(forming a solid with 20 equal triangular sides)
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Which viruses use the viral genome as mRNA?
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+ stranded, RNA viruses. Neg stranded must make a transcript of genome RNA 1st to use as a message and carry an RNA transcriptase in virus particle to perform this function.
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What is single order of Mononegavirales and their four families
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They have similar genomes and mode of replication.
Paramyxoviridae, Rhabdoviridae and Filoviridae |
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What is a Bacteriophages
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very small virus that infects most, perhaps all, bacteria.
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What are Viroids
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v. small, circular ssRNA molecule. They infect plants only, where may cause important diseases.
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Where are viral proteins produced in the cell?
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Ribosomes
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What happens in intracellular lysosomes?
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balloon like structures in which intracellular digestion occurs
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What surrounds outside of human cell
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lipid bilayer Plasma membrane
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What information is used to make a protein and what is process called?
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mRNAs from DNA are the transcription process and the process is called translation.
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What is a codon
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Each group of three consecutive nucleotides in mRNA, each specifying one protein.
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Describe process of ds RNA
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dsRNA ~ mRNA ~ -RNA+ mRNA= dsRNA
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What are characteristics of dsRNA viruses
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1. replication in cytoplasm
2. incoming virus particle only partially uncoated(remains intact and always ass with genomic RNA) 3.Activates enzymes which synthesize mRNA from each genome fragment |
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Describe +RNA virus process
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+RNA(mRNA) ~ -RNA ~ mRNA
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Describe +RNA characteristics and processes
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1. replicate in cytoplasm
2. naked RNA infectious 3. can produce single genomic or sub-genomic mRNAs |
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Describe -RNA viruses
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-RNA ~ virion complementary (vc)RNA ~ -RNA
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describe characteristics of -RNA Virus
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1. enveloped
2. helical nucleocapsid(remains intact and always ass with genomic RNA, like dsRNA viruses) 3. Replciation in cyto (x influenza virus) 4. Naked RNA NOT infectious 5. vcRNA is plus sense, but not translated |
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What is Ambisense viruses
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1. -RNA ~ vcRNA ~ -RNA
2. -RNA ~ vcRNA ~ mRNA 3. mRNA syn from genome and anti-genome 4. neither gen or anti-gen serves as mRNA 5. Delays synthesis of mRNA made from anti-genome 6. otherwise same as -RNA virus |
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Describe RNA retrovirus process and characteristics
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ssRNA(mRNA)~dsDNA~RNA
1. enveloped 2. Virion contains reverse transcriptase(RT) and RNase 3. Replication steps in both cytoplasm and nucleu. |
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Describe difference between replication of viruses and bacteria at the early cellular level
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Bacteria retain their structure and infectivity thruout growth cycle.
viruses lose their physical identity and most or all of their infectivity during inital stage of replication! |
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What is this initial stage of replication called for Virus and why
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ECLIPSE phase - virus loses identity and infectivity
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What is next stage after Eclipse phase in viral reproduction?
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PRODUCTIVE PHASE - full of new virus particles being produced and released into cell.
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What are cell functions required for virus replication and expression in DNA viruses?
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1. have small genomes and thus cannot encode for all nec functions.
2. DNA viruses a. can use all cell's machinery or can encode own polymerase (esp lg viruses) b. Almost all encode a protein for recog of origin of DNA replica c. Effect on cell permissivity and host range |
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Cell functions req for virus replication and expression in RNA viruses
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1. must encode at least RNA polymerase (since no cellular RNA-dep RNA polymerase exists)
2. RNA polymerase + proteins(viral and cell encoded)=RNA replicase complex. This recognizes promoters in viral RNA as starting point for RNA synthesis |
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Cell functions req for virus replication and expression regarding TRANSLATION
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1. mRNA translated by cellular ribosomes
2. cellular mRNAs usually have polyadenylated cap 3. |
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What is 'fusion protein' and give examples
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Hydrophobic aa which mediates fusion between lipids of virus and lipdis in cell membrane.
paramyxo(measles and mumps) and HIV have this |
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What is most common cellular entry technique for Viruses
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Cellular protein, clathrin, forms a so-called COATED PIT and once virus attaches, inversino of cellular membrand and ass virus occurs.
example - influenza |
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Talk about Translation
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1. mRNAs translated by cellular ribosomes
2. cellular mRNAs usually have polyadenylated cap 3. some mRNAs have no cap 4. long open reading frame(ORF) with intermittent stop codons 5. Early translation - enzymes 6. late translation - struc proteins & those needed for replication of genome |
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Talk about long ORF
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1. indiv proteins
2. polyproteins - read thru a. insertion b. ribosomal frame shifting i. slippery seq ii. structuralfeature(hairpin) iii. can be altered by mut. |
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Describe a + stranded RNA and features
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polio - acts as mRNA
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What is Baltimore scheme
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seven viral genome coding strategies (ssDNA, dsDNa, etc)
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What happens in early translation and then in late translation?
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Early - enzymes
late - structural proteins and those needed for replication of genome |
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What are Syncytia?
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formation of multinucleated giant cells (by paramyxoviruses (RSV), parainfluenza viruses and measles. Also Herpes and retro give rise to syncytia.
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routes of infection with viruses:
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fecal-oral or via mucous membranes, sexually transmitted, transplants.
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Penetration of viruses:
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A.non-env viruses;
1. protein conformational change(pH mediated?) 2. Internalization may b of: a. entire nucleocapsid b. sub-viral particle c. naked nucleic acid B. Enveloped viruses 1. Activation of fusion particle 2. Fusion w cellular membrane by: a. plasma mem b. Endosomal memb - endocytosis thru clathrin-coated vesicles. |
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Types of Lysis once virus infects
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Active Lysis:
1. Apoptosis - no inflammation 2. necrosis - inflammation |
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What else can happen (besides eclipse and lysis) when virus infects cell?
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1. latent infection w/o replication - herpes
2. persisten viral replicat w/o obvious effect on cell (HTLV 1 &2) 3. Chronic lysis w some survive to develop persistent infection(HIV) 4. Transformation -dereg cell cycle = immortality or oncogenesis(oncogene inc into viral genome) |
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what are degrees of viral replication in the cell
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1. permissive
2. semi-permissive 3. non-permissive |
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define virulence vs pathogenicity
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Virulence compares severity of ds caused by different strains of same organism.
Pathogenicity compares severity of ds caused by different micro orgs. |
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What is infectious dose
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amount to cause infection
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What is reproduction number
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number who could be infected by 1 person 12-15 are hi #s.
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What are localized infections
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upper resp - colds
lower respir - pneumonia (lungs/bronchi) liver - hepatitis |
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Describe path of generalized infection
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1entry virion thru epithelial surface, limited replication
2. migrate to reg lymph nodes - uptake by macrophages/monocytes 3. primary viremia (can have prodromal phase - fever malaise) 4. delivery to: a. RES - hi replication b. other organs via monocytes 5. secondary viremia - delivery ot target organ |
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notes on low Ag or ABY levels at certain stages for lab purposes in identifying pathogen
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early clinical signs - PCR to catch AGN in Viremia
ABYs - IgM 1st showing body response Aby later - IgG - had at one time, may not be current infection. |
