Term
True or False:
Viruses are non-motile and always require host machinery for viral protein synthesis |
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Definition
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Term
What are the 2 different types of symmetry exhibited by viral capsids, and how does this symmetry relate to whether the virus in enveloped or not? |
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Definition
1) Helical (Ebola)- animal viruses have envelopes
2) Spherical with icosahedral (HSV)- Can be either enveloped or not. |
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Term
What are the 7 families of DNA Viruses, and which are enveloped/not enveloped |
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Definition
HHAPPPI
1) Hepadna (envelope) 2) Herpes (envelope) 3) Adeno 4) Pox (envelope) 5) Papova 6) Parvo (ssDNA) 7) Irido (envelope) |
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Term
Which DNA viruses have circular DNA? |
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Definition
Papovavirus and Hepadnavirus |
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Term
Which family of DNA viruses have helical capsids and replicate in the cytoplasm? |
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Definition
Pox Viruses (enveloped)!
All other DNA viruses replicate in the nucleus and have icosahedral symetry |
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Term
Which enveloped DNA viruses are dsDNA viruses? |
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Definition
Herpesviridae (linear), Irido (linear) and Hepadnaviridae (circular)
**Poxviradae is a complex, envelope DNA virus** |
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Term
What are the 2 non-enveloped dsDNA viruses? |
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Definition
Papovavirus (circular)
Adenovirus (linear) |
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Term
What is the only ssDNA virus (it is also nonenveloped)? |
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Definition
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Term
What are the 4 classes of RNA viruses? |
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Definition
1) ss(+) RNA (6)
2) ss(-) (3)
3) Segmented ss(-) (3)
4) Segmented dsRNA reovirus |
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Term
What type of virus is Rotavirus? |
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Definition
It is a reovirus, which is the only family of segmented dsRNA viruses |
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Term
What are the 6 families of ss (+) RNA viruses and which are enveloped/nonenveloped? |
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Definition
Enveloped 1) Togavirus (rubella) 2) Coronavirus (SARS) 3) Flavivirus (West nile/ Dengue) 4) Retrovirus (HIV, HTLV)
NONENVELOPED 1) Picornavirus (Polio, HepA, Rhino) 2) Calicivirus (Norovirus) |
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Term
What are the 6 families of enveloped ss(-) RNA viruses and which are segmented? |
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Definition
SEGMENTED 1) Arenavirus (Lasa fever) 2) Bunyavirus (Hantavirus) 3) Orthomyxovirus (Influenza)
NONSEGMENTED 1) Filovirus (Ebola) 2) Paramyxovirus (RSV, Measles, Mumps) 3) Rhabdovirus (Rabies) |
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Term
What type of virus causes Rabies (Rhabdo), Ebola (Filo) and Mumps/Measles (Paramyxo)? |
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Definition
Enveloped, non-segmented ssRNA (-) virus. |
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Term
What type of virus causes Influenza (Orthomyxo) and Lasa Fever (Arena)? |
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Definition
Enveloped, Segmented ssRNA (-) Viruses. |
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Term
What type of virus causes Rubella (Toga), SARS (Corona) and HIV (Retro)? |
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Definition
Enveloped, ssRNA(+) Virus |
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Term
What type of virus causes Polio, HepA (Picorna) and Norovirus (Calici) |
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Definition
Non-enveloped, ssRNA(+) Viruses |
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Term
What are the 7 primary steps in the life cycle of a typical virus? |
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Definition
1) Attachment (cell-surface protein to viral receptor)
2) Penetration (fusion/endocytosis)
3) Un-coating (release viral genome from capsid)
4) Gene expression (synthesis of viral proteins)
5) Replication (synthesis of viral nucleic acid)
6) Assembly (takes place in inclusion bodies)
7) Release (death of infected cell may or may not occur) |
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Term
How does the influenza virus gain access to host cells? |
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Definition
This segmented, enveloped ssRNA(-) virus has Hemagglutinin (HA) protein which binds to sialic acid on host, enabling both attachment and penetration. |
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Term
What is the role of Neurominidase in influenza infection? |
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Definition
This enzyme cleaves sialic acid and is critical for viral egression following assembly (remember that SA was required for attachment/penetration) |
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Term
How can enveloped viruses exit infected cells? |
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Definition
1) Budding through plasma membrane
2) Fusion of secretory vesicles containing virus particles with plasma membrane
**Non-enveloped viruses usually lyse cells) |
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Term
How does Parvovirus replicate within a host cell? |
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Definition
This ssDNA virus is the only virus to use the host cell machinery to replicate their DNA (all viruses use host for viral protein synthesis).
**All other viruses have their own viral polymerase** |
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Term
How does Pox virus replicate within the host cell? |
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Definition
- This complex, enveloped dsDNA virus is the only DNA virus that replicates in the cytoplasm
- They have their own DNA and RNA polymerases, as well as enzymes for capping and poly A addition |
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Term
How does Influenza virus replicate within the host cell? |
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Definition
This segmented, enveloped ssRNA (-) virus is the only RNA virus to replicate their RNA genomes and make mRNAs in the nucleus (all others do so in the cytoplasm). |
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Term
What type of polymerase in the Reverse Transcriptase utilized by HIV? |
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Definition
RNA-dependent DNA polymerase (RdDp) |
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Term
What type of polymerase do RNA viruses use? |
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Definition
RNA-dependent RNA polymerase (RdRp) |
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Term
Explain how Viral Genome replication occurs in DNA viruses? |
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Definition
1) Encode own viral DNA polymerase (except Parvovirus), which is more efficient than host polymerase
2) Early viral proteins are synthesized in the nucleus (except for Pox virus), which cue DNA replication (i.e. viral polymerase)
3) Late Viral protein synthesis occurs (viral structure and assembly) |
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Term
What is different about DNA replication in larger DNA viruses such as herpes virus? |
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Definition
More stages
1) Immediate early (alpha) stage of protein synthesis is for early protein synthesis
2) Early (beta) stage is to allow replication
3) Late (gamma) stage follows replication and is for structure. |
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Term
True or False:
The genomes of all RNA viruses, except for retroviruses, encode an RdRp. to catalyze the synthesis of new genomes and mRNA |
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Definition
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Term
How does replication occur is ssRNA(+) viruses such as Togavirus (rubella), Coronavirus (SARS) and Flavivirus (Dengue, West Nile) |
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Definition
1) Viral RNA genome is brought in with virus and can function as mRNA to make early protein products such as RdRp
2) Viral RNA Poli makes complementary copies of viral genome (-RNA), which are used for translation of viral proteins
3) Some of viral (+) RNA that is made is packaged into new virus particles |
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Term
How does replication occur is ssRNA(-) viruses such as Rhabovirus (rabies) and Paramyxovirus (mumps/measles)? |
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Definition
1) (-) RNA is converted to (+) RNA with RNA poli brough into cells as PART OF VIRUS PARTICLE
2) Viral (+) RNA are translated by host cell machinery to make capsid, envelope, polymerase ect.
3) RNA poli makes (-) RNA which is packaged into virus particles along with RNA poli to generate new infections. |
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Term
How do segmented ssRNA(-) viruses such as orthomyxovirus (influenza) and arenavirus (Lasa fever) replicate in host cells? |
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Definition
The same way that other (-)RNA viruses do, but they can SWAP RNA SEGMENTS (reassortment) |
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Term
How do retroviruses replicate? |
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Definition
1) In the cytoplasm, RdDp (RT) within a viral particle containing (+) RNA makes a RNA/DNA hybrid.
2) The RNA/DNA hybrid becomes dsDNA via RT
3) dsDNA is integrated into host cell DNA with viral integrase (also in original viral particle)
4) Replication and transcription occur using host enzymes
5) Viral proteins are translated (RdRp, integrase, capsid, protease) and packaged for eggression. |
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Term
What is the unique mechanism of replication exhibited by Hepatitis B virus? |
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Definition
Hepatna viruses are enveloped DNA viruses that have circular genomes ad gapped DNA
1) Gapped DNA is repaired in nuclear
2) Viral mRNA and pregenomic RNA are made using host cell machinery
3) Pregenomic RNA is exported to cytoplasm where it serves as template for RT to form dsDNA within newly forms viral particles
**need a threshold among of envelope proteins before release can take place** |
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Term
How do non-enveloped viruses exit infected cells? |
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Definition
Viruses such as Picornavirus (HPA, Polio), Cacilcivirus (Norovirus), and Adenovirus exit cells via cell lysis |
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