Lecture 1: introduction Flashcards
What is a virus?
a virus is a filterable, small obligate intracellular parasite that is inert outside of a host cell
what does propagation of viruses depend on
specialized host cells that supply the metabolic and biosynthetic machinery of eukaryotic or prokaryotic cells
T/F: viruses lack organelles
True. the only pseudo-exception to this is Arenavirus, which acquires ribosomes from the host cells. These ribosomes are not functional
If you wanted to observe a virus, which of the following strategies could you use?
a) electron microscopy
b)nanoscopy
c) light microscopy
d) naked eye
Electron microscopy and/or nanoscopy
What is the biggest virus, and what is the smallest?
pithovirus sibericum is the largest, at 1.5 micrometers.
Circovirus is the smallest at 17 nm
what was the pasteur-chamberland filter?
A filter created in 1890 that allowed for bacteria and other cells to be removed from a lliquid. It worked by having pores of 100-1000 nm for filtering purposes
What are the three structural components of a virus?
- the genome
- capsid coat made 100% of protein
- +/- an envelope consisting of a lipid bilayer
Describe viral envelop formation
modified host cell membranes surrounds the capsid.
what is the viral envelop made of
lipid bilayer that is studded with virus-coded glycosylated membrane proteins
what do budding viruses carry?
certain host cell proteins that form integral constituents of the viral envelope
what is a bacteriophage?
a virus that infects bacteria. It consists of a head made from protein and DNA, and a tail of solely protein
What virus is commonly used as a vector to deliver antigens?
poxvirus
what is the largest animal virus?
poxviruses
70% of all viruses are ___ viruses
RNA
What are the two types of viral genomes?
Single-coil and fragmented
what is the implication of having a segmented genome in a virus?
mispackaging and subtypes from replication of the fragments
Give an example of a virus with a single-coil genome
Respiratory syncytial virus
give an example of a virus with a fragmented genome
rotavirus
Go review the central dogma if you’ve forgotten it
good stuff
what was the first classification system for viruses
Linnaean hierarchical system
What did the international committee on taxonomy of viruses (ICTV) deem was wrong with using the Linnaean system for viruses?
Viruses have small genomes and a high mutation rate, making it difficult to classify them beyond order. Because of this, viruses should not be classified on phylum or class
how many orders of viruses have been established by the ICTV
7
Of the 7 orders of viruses described by the ICTV, which are the 3 that you should know?
Caudovirales-tailed dsDNA bacteriophages
Ligamenvirales-linear, dsDNA archaean viruses
Tymovirales-monopartite (+) ssRNA viruses that infect plants
What does the Baltimore classification base its classification system on
the mechanism of mRNA production
Name the seven groups of viruses in Baltimore classification
- dsDNA
- ssDNA
- dsRNA
- (+) ssRNA
- (-)ssRNA
- ssRNA-RT
- dsDNA-RT
Pathogenesis of mRNA synthesis in dsDNA viruses (excepting pox)
dsDNA -> cellular RNA polymerase 2 -> mRNA (+)
what is the only dsDNA virus that uses virion transcriptase as opposed to cellular RNA poly 2?
asfa, irido, and (most importantly) pox
describe the pathway of mRNA synthesis for pox viruses
Pox dsDNA -> virion transcriptase -> mRNA (+)
describe the pathway of mRNA synthesis in ssDNA
ssDNA->cellular DNA polymerase -> dsDNA -> cellular RNA polymerase 2 -> mRNA (+)
what are some examples of dsDNA viruses
Adeno
Hepadna
Herpes
Papilloma
polyoma
Asfa
Irido
Pox
what are some examples of ssDNA
Anello
Circo
parvo
describe the pathway of primary mRNA synthesis by ssRNA (+) (excepting retroviruses)
the ssRNA (+) acts as the mRNA (+), and doesn’t have to undergo any transformation
describe the pathway of mRNA synthesis by retroviruses (ssRNA (+))
retro -> virion reverse transcriptase -> ssDNA -> integrates with host genome -> cellular poly 2 -> mRNA (+)
describe the pathway of mRNA synthesis by dsRNA
dsRNA -> virion RdRp -> mRNA (+)
describe the pathway of mRNA by ssRNA (-) (excepting delta)
ssRNA (-) ->virion RdRp ->mRNA (+)
pathway of mRNA by deltaviruses
Delta ->cellular RNA poly 2 -> mRNA (+)
what are some examples of ssRNA (+)
picona
Flavi
calici
astro
corona
retro
what are some examples of dsRNA viruses
reo
birna
What are some examples of ssRNA (-) viruses
rabdo
filo
borna
paramyxo
orthomyxo
bunya
delta
