Which are the 4 criteria of a microorganism to be considered a virus?
1. Only one type of NA (DNA or RNA) 2. It can’t growth or divide 3. Obligate intracellular paratisism 4. A define structure
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What does it mean when we say viruses obligate intracellular paratisism?
Because they lack of enzymatic or energetic systems they are using the cell to replicate.
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What is the virion?
Mature, infectious, extracellular viral particle
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What does the virion contain?
It contains:
\-genome
\-capsid
(-envelope)
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Which are the charcteristics of the DNA genomes?
1. genome size is variable 2. most often 3D 2-stranded and linear
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Please tell me one example of 1. single stranded DNA virus 2. Double stranded (a. linear, b.circular) 3. partially double stranded
1. parvoviridae 2. a. adenoviridae b. papillomaviridae, 3. Hepadnaviridae
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Which are the charcteristics of the RNA genomes?
1. Needs a viral RNA dependent RNA polymerase to replicate 2. Most often single-stranded and linear
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Please tell me one example of 1. single stranded RNA virus (a. diploid b. linear, b. segmented) 2. Double stranded (segmented)
1. a. retroviridae b. coronaviridae, c. orthomyxoviridae 2. reoviridae
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In what RNA genomes are divided?
1. Positive-strand: can act as mRNA and can immediately translated into proteins (coronavirus) 2. Negative-strand: has to be trancribed first (influenza virus)
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Which are the special characistics of the RNA genome?
1. A cap at the 5’ terminal end 2. A poly-A Sequence at the 3’ terminal end 3. A viral protein covalently attached to the 5′ end acts as a primer during RNA synthesis (Picornaviridae)
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Which are the roles of capsids?
1. Protect the genome from the environment 2. For naked viruses, take part in the attachment of the virus to the host cell.
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Tell me the characteristics of the viral capsid.
1. Resistant and very stable structure 2. Limited viral genome coding capacity 3. Principe of self-assembly
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How capsid is formed?
By polymerization of 1 or a small number of proteins.
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Which are the 2 main shapes of capsid?
1. Tubular capsid with helical symmetry 2. Icosahedral capsid with cubic symmetry
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Helical capsid: most of them are _____-sense RNA virus.
Negative
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All helical animal viruses are ________.
Enveloped
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Envelope: 1. from what they are composed of? 2. are they stable?
1. Complex composition with lipids and glycoproteins. 2. Very sensitive to physico-chemical actions and to environmental conditions.
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How do viruses aquire their envelope?
By budding through a cellular membrane.
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What are spikes?
Projections verticle to the surface.
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What is the HIV1 spike (monomera, dimer, trimer)?
Trimer
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How do we classify a virus?
1. Species 2. Genus 3. Family 4. Order 5. Class 6. Phylum 7. Kingdom
or baltimore classification
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Which are the different steps in the viral replication cycle?