ch 17 Flashcards
viruses characteristics
non motile, rna or dna, acellular, visible under electron microscopy, not alive, small asf, abundant
capsid
portion coat, may have spikes
obligate intracellular parasite
must replicate inside host
what can viruses infect
all living organisms
strains
differ in virulence and antigenic properties
varient
altered genotype, but does same thing
virus classified
host, size and shape, envelope, nucleic acid, disease caused
host range is determined by
specific host attachment sites and cell factors for multiplication
zoonosis
animal virus that jumps to human
virion
ready to infect host cell
virion parts
nucleic acid- DNA/RNA, singe or double, linear or circular
protein coat- capsid
envelope- extra capsid layer (maybe), from host
nuceleocapsid
nucleic acid plus capsid
spikes on viruses are - for -
spiky protein for attachment
capsid shapes
icosahedral or helical
enveloped viruses appear
spherical
how to viruses acquire envelopes
steal plasma membrane and proteins from host
budding
developing a virion
complex viruses
capsid with additional structures
ex bacteriophage
helical virus
polyhedral virus
Many sided – 20 equilateral triangular faces
– Example: adenovirus and poliovirus
virions encode info to make proteins for
structure, attachment, replication modifications of nucleic acids
class I
dsDNA
class II
ssDNA
class III
dsRNA
class IV
+ssRNA
class V
-ssRNA
class VI
ssRNA-RT
class VII
dsDNA-RT
positive nucleic acid polarity
virus can act as mRNA
-viridae
virus family name
viral species
“common name”
group of viruses sharing the same genetic info and ecological niche
virus infection cycle
1.attachment/absorption
2.entry- fusion/endocytosis
3. uncoating
4. biosynthesis- make parts
5. maturation- assemble
6.release
eclipse periods
bn attachment and release
If host has high glucose, virus will be
lytic (replicate in cell, take over, go crazy)
If host has low glucose, virus will be
lysogenic (incorporate into genome)
animal virus cell attachment
bind to receptor on host (glycolipids or glycoproteins)
dsDNA virus
use host cell machinery directly, need to enter nucleus
episomes
circular DNA, virus genome integrated into host DNA
ssDNA
use host cell machinery directly, replicates ssDNA to dsDNA, ssDNA for progeny
dsRNA
need RNA replicase
replicated as dsRNA
ssRNA
need RNA replicase
ssRNA- template to make ssRNA+ for progeny
occurs in cytoplasm
release via
budding or rupture
easiest ways to repent viral infection
behavior and vaccination
antivirals
not many, target unique viral structure
RNA virus mutation rate
higher than DNA viruses
drugs (3) that target HIV inhibit
intergrase, entry, reverse transcription, protease
detecting viruses via counting
grow and look for plaques and cytopathic effects
negri bodies (for rabies and such)
staining inclusion
serotyping
antibody test for antibodies
molecular methods for viral detection
DNA hybridization, PCR, RT-PCR
Genus names end in
-virus
treating viruses
Preventing infections (best option?)
– Vaccination
– Behavior
AND DRUGS THAT TARGET STRUCTURE
