Chapter 1 Flashcards
who is the father of virology?
dimitri ivanovsky
Dimitri Ivanovsky did what?
- Russian biologist (botanist)
- Reported that the infectious component of tobacco mosaic disease could pass through a porcelain filter that removed bacteria and fungi (1892)
- “filter-passing”
- Did not isolate a virus particle
who is martinus Beijerinck?
- Dutch microbiologist and botanist
infectious agent could replicate in plants, therefore not a toxin (1898) - Used the term
- Contagium vivum fluidim (infectious living liquid) to describe his findings
who was Ernst Ruska?
- german physicist
- visualization of viruses didn’t occur till 1930s with the microscopy advent of electron microscopes
how did yellow fever originate?
from africa, spread to the new world with slave trade
what was the first human disease whose causative agent was identified as a virus?
yellow fever
Jesse William Lazear preformed what two tests?
- Volunteers slept in clothes and beds of yellow fever patients (but had mosquito nets) (did not get sick)
- Volunteers stayed away from patients but were exposed to mosquitoes that fed on yellow fever patients
(all got sick)
yellow fever was spread by?
insect vector
you need____ and ___ cells to culture viruses
live and replicating
what is a virus?
- A subcellular ‘organism’ with a parasitic life cycle
- Needs a host cell to replicate
- Has no metabolic activity outside of the host cell
a virus’s infection may be lytic or latent meaning?
lytic (causing cell death)
latent (viral genome remains dormant in host cell)
oncogenic
cancer causing
what are the abilities that prove viruses to be alive
- Ability to replicate
- Evolve
- Contain nucleic acids
what are the abilities that prove viruses not to be alive
- Energy production
- Respiration
- Response to negative environments
- Locomotion
- Growth
virus particles bind to ____ cells
target
viral genome replicates _____ the cell
within
what is the viron?
- virus particle, a single infectious agent
- Made of nucleic acid genome (DNA or RNA) protected by a protein shell
what is the capsid?
protein structure surrounding viral genome
Capsomers
repeating protein subunits that form the capsid
envelope
derived from host cell lipid bilayer, covers virus capsid
Nucleoproteins
proteins that surround the viral genome (either structural or replicative proteins)
Nucleocapsid
nucleic acids, structural, and replicative proteins
what is a tegument?
Thick group of proteins underneath envelope
enveloped virus:
- RNA genome
- Nucleoproteins
- Nucleocapsid
- Capsid
- Envelope
- Glycoproteins
non enveloped virus:
- DNA genome
- Nucleoproteins
- Capsid
- Nucleocapsid
what are the 4 standard morphological groups?
- non enveloped /helical capsid
- non enveloped/ icosahedral capsid
- enveloped/ helical capsid
- enveloped/icosahedral capsid
How is the capsid formed?
repeating protein subunits (capsomers)
capsids arent capable of self assembly (T F)
false, they are
what is the morphology of capsids?
helical or complex
describe icosahedral symmetry
symmetry is based on the presence of the correct axes of symmetry
- 2 fold axes of rotational symmetry about the face edge
- 3 fold axes of rotational symmetry about the face centre
- 5 fold axes of rotational symmetry about the face vertex
what is the symmetry of picornovirus?
dodecahedron
what is the symmetry of adenovirus?
hexameric
the picornavirus is a __________ capsid protein
4 (VP1 VP2 VP3 VP4)
the adenovirus is made up of __________ hexon subunits
and ____________ proteins in total
20, 11
the poxvirus has a very _______ genome and expresses more than 100 proteins
large
`the flivovirus has a ____ nucleocapsid
helical
when was the last outbreak of smallpox?
1997
*what did jesse lazear determine was the vector of yellow fever?
mosquitos
the virus envelope is derived from the __________ _________
host membrane
viral glycoproteins are ________
hydrophilic
lipids cannot be inserted into the envelope (T F)
false (they can)
lipids cannot be inserted into the envelope (T F)
false (they can)
the viral genome has eirther _____or _____
DNA or RNA but not both
can the viral genome be single or double stranded?
yes
viruses are the only known form of life that can have a genome made of RNA (T F)
T
the genome size is related to the ________ of the virus
complexity
____ has one of the largest genomes that can infect humans?
poxvirus
_________ has the smallest genome infecting humans
parvovirus
_________ has the smallest genome infecting humans
parvovirus
viruses use ________ to maximize functionality from limited genome sequence
frameshifting
each amino acid is encoded by 3 bases called a ____
codon
what is RNA splicing?
cut and joins viral mRNA to produce different proteins from one original RNA molecule
even in the largest virus genome _______ codes for proteins
90%
DNA viruses are replicated by _____ processes or _____ processes
cellular or simple
DNA viruses form replication centers in what 2 places?
cytoplasm or nucleus
what do host DNA polymerases do?
check the sequence
for RNA viruses replication usually involves _____ cell machinery
host
are RNA viruses proofread?
no
RNA viruses have a ______ mutation rate
high
RNA viruses have a _______ genome to decrease the mutation rate
segemnted
what is antigenic drift and which viruses use it?
RNA viruses use to confer immune escape advantage
*A larger genome means more complex virus ( T F)
T
HIV is one of the most rapidly ________ viruses
changing
is HIV segmented
non segmented
is HIV segmented
non segmented
HIV has a ____ genome
diploid
what are the 4 hypothesis for HIV mutation rates?
- reverse transcriptase is a low fidelity polymerase, each genome copy will be different from its parental template
- Reverse transcriptase jumping from one genome to the other could introduce errors
- Multiple HIV particles infecting the same cell, genomes could reassort
- Recombination during DNa integration and excision, recombination rate would be high
what is the result of HIV mutation rates?
incredible immune invasion capabilities
what is the result of HIV mutation rates?
incredible immune invasion capabilities
does every ifnection cause disease?
no
describe the effect infection causing disease?
mostly observed in viruses who have jumped to new host
- some symptoms cause imune response, ex. ebola
what is asymptomatic ?
no symptoms or flare ups
- latent HSV 1
what is asymptomatic ?
no symptoms or flare ups
- latent HSV 1
describe how viruses modulate the host cell?
- take over protein synthesis machinery
- have mechanisms to maike host cell recognize viral mRNA
- control the immune response
what are the types of virus infection?
- transforming
- latent
- acute
- chronic
describe a lytic infection:
- cell lysis following production of viral particles
- rapid cell death
what causes cell lysis?
- viral enzymes
- indirect damage of producing so many viral particles
- breakdown of membrane integrity
describe persistent or chronic infections:
Infections that produce small amounts of virus over a long period of time because the immune system doesnt recognize viral antigens
ex. hep B hep C
describe a latent infection
viral genome is present but not active within the cell, only a small portion of viral genome is active
there is __ RNA LAT involved in the reactivation of HSV 1
3
what is a provirus?
the genetic material of a virus is incorporated into and able to replicate as part of the genome of a host cell
what is oncogenesis?
- loss of regulation of cell growth
- Changes to cell appearance and structure
- Abnormal chromosome numbers (aneuploidy)
- Altered transcription and production of growth factors
- Uninhibited cell growth
what is retroviridae?
viruses can insert their genome into the hosts causing mutations
