General Virology 1 Flashcards
What is a virus?
A filterable agent, a small obligate intracellular “parasite” that is inert outside of host cells.
Can viruses have RNA and DNA genomes?
NO! One or the other
Propagation of viruses depends on what?
The specialized host cells that supply the metabolic and biosynthetic machinery of prokaryotic and eukaryotic cells
Do viruses have functional ribosomes?
No they steal ribosomes from other cells (same with other organelles)
Name 3 difference between bacteria and viruses
Example of virus that internalizes ribosomes
Arenavirus
Can you see virus with a light microscope?
No, need electron microscope or Nanoscopy
Size range of viruses
17 nm (circovirus) to 250 nm (small pox)
What are the two forms of viruses?
Naked and enveloped
Describe a Naked virus
A genome (DNA or RNA) protected by a capsid (capsid is 100% protein)
-May have spike proteins
what is a nucleocapsid?
The capsid and genome
Function of the capsid?
Acts as a shell to protect the viral genome from nucleases
Describe enveloped viruses
A host derived lipid bilayer, that closely surrounds the viral capsid and genome. The exterior of the bilayer is studded with glycosylated (trans-) membrane proteins
Why are glycosylated proteins important?
They help determine what hosts the virus can invade and antigenic composition of the virus
Budding viruses contain what?
They carry host cells proteins that are integral constants of their viral envelope (Why not easily detected by immune system)
Which virus type more vulnerable to soap?
Envelope b/c made of lipid bilayer that soap breaks down (naked virus needs stronger cleaners)
What is the largest virus?
Pithovirus (only infects amoebas)
Mimivirus and pandora virus are also large
pandora virus has the largest genome
What is the largest animal virus?
Poxviruses
What is the smallest viruses?
Circoviruses (makes only 2 proteins)
What is a bacteriophage? Describe its structure
A virus that infects and replicates within bacteria and archaea
Has a head which contains protein and DNA and a tail that contains only proteins
Name the 6 viral shapes and give an example of each
1) Elongated- E.coli
2) Dumbell- pox. virus
3) Crown like- covid viruses (enveloped)
4) Bullet shape- Rabies
5) Rotovirus
6) Naked- Adenovirus
What is the implication of having a segmented genome in a virus?
Because little segments can get packed up into different viruses and replicate. They reassort into new strains (1 and 2 can combine to make 3) These new strains that can evade the immune system. This is called reassortment. It causes the Spanish influenza, (has swine human and avian origin)
Name basic steps and enzymes involved in the central dogma
Name the two classification systems for viruses
International Committee on Taxonomy on Viruses (ICTV)
Baltimore Classification
Describe the ICTV classification system
Viruses classified on order, family, subfamily, genus and species
Not phylum or class since their small genome size and mutation rate make it difficult to determine ancestry beyond order
What are virus suffixes for order, family, subfamily, genus and species
Order: -virales
Family: -viridae
Subfamily: -virinae
Genus: -virus
Species: -virus
How many orders are there in the ICTV system?
7
Name the 7 ICTV classes and characteristics about them
1) Caudovirales- tailed dsDNA bacteriophages (does not infect animals)
2) Herpesvirales-large eukaryotic dsDNA viruses
3) Ligamenvirales-linear, dsDNA, archaean viruses (does not infect animals)
4) Mononegavirales-nonsegmented (-) strand ssRNA, plant and animal viruses
5) Nidovirales- (+) strand ssRNA, vertebrate viruses
6) Picornavirales-small (+) strand ssRNA viruses that infect a variety of plant, insect and animal hosts
7) Tymovirales-monopartite (+) ssRNA viruses that infect plants (does not infect animals)
Describe the Baltimore classification system
Used in conjunction with ICTV and is based on the mechanism of mRNA production (transcription), different mechanisms are used to achieve each family
How many groups are there in the Baltimore system?
7
What are the 7 Baltimore groups and their descriptors?
I: dsDNA viruses (e.g. Adeno, Herpes, Pox)
II: ssDNA viruses (+ sense) DNA (e.g. Parvoviruses)
III: dsRNA viruses (e.g. Reoviruses)
IV: (+)ssRNA viruses (e.g. Picornaviruses, Togaviruses)
V: (−)ssRNA viruses (e.g. Orthomyxoviruses, Rhabdoviruses)
VI: ssRNA-RT viruses (+ sense) RNA with DNA intermediate in life-cycle (e.g. Retroviruses)
VII: dsDNA-RT viruses (e.g. Hepadnaviruses)
What does the + or - mean?
Defines the polarity compared to mRNA, which defines how they are translated by ribosomes
+ ssRNA use their own viral RNA genome as mRNA
-ssRNA uses RNA dependant RNA polymerase from the viron
Give an example of a group 1 virus
dsDNA viruses
e.g. Adeno, Herpes, Pox
Give an example of a group 2 virus
ssDNA viruses (+ sense) DNA
e.g. Parvoviruses
Give an example of a group 3 virus
dsRNA viruses
e.g. Reoviruses
Give an example of a group 4 virus
(+)ssRNA viruses
e.g. Picornaviruses, Togaviruses
Give an example of a group 5 virus
(−)ssRNA viruses
(e.g. Orthomyxoviruses, Rhabdoviruses)
Give an example of a group 6 virus
ssRNA-RT viruses (+ sense) RNA with DNA intermediate in life-cycle
(e.g. Retroviruses)
Give an example of a group 7 virus
dsDNA-RT viruses
(e.g. Hepadnaviruses)
Example of DNA envoloped virus
Poxviradae (pox viruses)
Example of DNA naked virus
Parvovirade (parvo viruses)
Example of enveloped RNA virus
Influenza Virus
Cornaviradae
Example of naked RNA virus
Reoviridae (rotavirus)
70% of viruses are what?
RNA viruses
