lecture 1- intro Flashcards
what are characteristics that define a virus?
- small obligate intracellular parasites
- the propagation of viruses depends on specialized host cells supplying the complex metabolic and biosynthetic machinery
do viruses have organelles?
no
which is more resistant- enveloped or naked viruses? why?
Naked viruses are more resistant because soap would dissolve the lipid bilayer of enveloped viruses, thus inactivating them
what is the function of a capsid
shell to protect viral genome from nucleases
where is viral envelope derived from
host cell membranes (plasma, other)
exterior of envelope bilayer is studded with ___
glycosylated transmembrane proteins
importance of outer capsid and envelop proteins
determine host range and antigenic composition of virion
largest known virus? what does it infect?
Pithovirus infects amoebas
second largest virus
pandora virus
the head of a bacteriophage is made of…
protein and DNA
the tail of a bacteriophage is made of …
protein only
largest animal virus
poxvirus
smallest viruses? how many protein species?
circoviruses have 2 protein species
true or false: most viruses are DNA viruses
false - 70% are RNA
example of an enveloped DNA virus
herpesvirus
example of a naked DNA virus
adenovirus, parvo
example of an enveloped RNA virus
influenza
example of a naked DNA virus
parvovirus
implication of having segmented genome in the virus? give an example…
increased likelihood of reassortment, thus mutations
influenza virus is segmented so many variants might be packed together (spanish flu)
Linnaean hierarchical system
phylum
class
order
family
genus
species
ICTV stands for
international committee on taxonomy of viruses
what did the ICTV establish?
viruses should not be classified on the basis of phylum or class because their small genome size and high rate of mutation make it difficult to determine their ancestry beyond order
Order of virus
-virales
Family of virus
-viridae
Subfamily of virus
-virinae
Genus of virus
-virus
Species of virus
-virus
what are the 7 orders of viruses based on ICTV classification?
- Caudovirales
- Herpesvirales
- Ligamenvirales
- Mononegavirales
- Nidovirales
- Picornavirales
- Tymovirales
(cat herpes likely mean no pictures taken)
caudovirales
tailed dsDNA (group 1) bacteriophages
herpesvirales
large eukaryotic dsDNA viruses
ligamenvirales
linear, dsDNA (group 1) archaean viruses
mononegavirales
nonsegmented (-) strand ssRNA (group V) plant and animal viruses
nidovirales
(+) strand ssRNA (group IV) vertebrate viruses
picornavirales
small (+) strand ssRNA viruses that infect a variety of plant, insect, and animal hosts
tymovirales
monoparasite (+) ssRNA viruses that infect plants
baltimore classification of viruses
I - VII
based on mechanism of mRNA production
Baltimore I? example?
dsDNA
(adeno, herpes, pox)
Baltimore II? example?
ssDNA (+ sense) DNA
(parvo)
Baltimore III? example?
dsRNA
(reoviruses)
Baltimore IV? example?
(+) ssRNA
(picornaviruses, togaviruses)
Baltimore V? example?
(-) ssRNA
(orthomyxoviruses, rhabdoviruses)
Baltimore VI? example?
ssRNA-RT (+ sense) RNA with intermediate in life-cycle
(retroviruses)
Baltimore VII? example?
dsDNA-RT
(hepadnaviruses)
pathway of primary mRNA synthesis for dsDNA viruses?
cellular RNA pol2 –> mRNA (+)
or
for pox, asfa, and irido:
Virion transcriptase –> mRNA (+)
pathway of primary mRNA synthesis for ssDNA viruses?
cellular DNA pol –> dsDNA –> cellular RNA pol2 –> mRNA (+)
pathway of primary mRNA synthesis for ssRNA (+) viruses?
viral genome act as mRNA –> mRNA (+)
or
for retro:
virion reverse transcriptase –> ssDNA –> cellular pol2 –> mRNA (+)
pathway of primary mRNA synthesis for ssDNA (-) viruses?
virion RdRp –> mRNA (+)
or
for delta:
cellular RNA pol2 –> mRNA (+)
pathway of primary mRNA synthesis for dsDNA viruses?
virion RdRp –> mRNA (+)
