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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