Exam 1 - Lecture 5 Flashcards
are viruses alive?
nah
what does a complete virion consist of?
- nucleic acid (genome)
- capsid (coat of protein)
what is a virus?
an infectious agent
true or false: viruses cannot exist extracellularly.
false, they can EXIST extracellularly but they can’t reproduce independent of a living host cell
what are some positives of viruses (what are some good things)?
- important members of the aquatic world
- important in evolution
- important model systems in biology
a virus that infects bacteria is called a:
bacteriophage
virions are composed of:
RNA only
satellites are composed of:
nucleic acids (DNA/RNA) only
prions are composed of:
proteins only
viruses are composed of:
nucleic acid and protein (capsid)
what is the size range of virion diameter?
10-400 nm
true or false: virions can have both DNA and RNA.
false
what is the nucleocapsid of a virion?
nucleic acid and a protein coat (capsid)
what are the roles of capsids?
- protect genetic material
- aid in genetic transfer between host cells
what are the protein subunits of the capsid called?
protomers
what are the two common shapes of capsids?
helical and icosahedral (20 sides)
what are the subunits of an icosahedral capsid called?
capsomers
what are the largest animal viruses?
poxviruses
large bacteriophages have binal symmetry. what does this mean?
the head is icosahedral, the tail is helical
some viruses have another layer called an envelope. where does this usually come from?
host cell membranes
what are viral spikes?
viral encoded proteins that project from the envelope surface
what is an example of viral spikes that attach to the host cell?
what about spikes that have enzymatic activity?
- hemagglutinin of influenza virus
- neuraminidase of influenza virus
what are the three enzymes found in HIV?
- reverse transcriptase
- integrase
- protease
true or false: viruses can have ssDNA genomes.
true
true or false: viruses can have linear (noncircular) genomes.
true
true of false: some viruses have 16S rRNA.
false, none do.
what is the common gene between all viruses?
there is none!
what are viruses that use reverse transcription called?
retroviruses
what direction do you read genomes in?
5’ to 3’
is the sense strand the plus- or negative-strand?
- plus-strand
(idk why its plus and negative and not plus and minus or pos and neg)
what are the seven Baltimore classification groups?
I: dsDNA
II: ssDNA (+)
III: dsRNA
IV: ssRNA (+)
V: ssRNA (-)
VI: ssRNA (RT) (+)
VII: dsDNA (RT)
RT means retrovirus
what are the five steps of viral multiplication?
- attachment
- entry and genome uncoating
- synthesis
- assembly
- release
how does attachment of the virus happen?
interaction between viral spikes (ligands) and the host cell receptors
what is tropism?
tissue specific receptor distribution
what are the three common methods of viral entry?
- fusion of viral envelope with host membrane
- endocytosis in a vesicle
- injection of nucleic acid
what is the synthesis stage of viral replication?
when the virion generates copies of itself
which of the following have to bring their own proteins necessary for synthesis and cannot use the preexisting host machinery: dsDNA or RNA viruses?
RNA viruses
true or false: all assembly takes place in the nucleus
false, some is in the nucleus, some in the cytoplasm, then they come together
which will lyse the cell upon release: enveloped or nonenveloped viruses?
how do they do it?
- nonenveloped viruses
- they have holin to create pores in the plasma membrane OR lysozymes that degrade peptidoglycan
how are enveloped viruses released from the cell?
budding: an envelope is derived from the host cell membrane
which form of viral release allows for the host cell to survive and continue releasing virions for some time?
budding
what is the name of the virus that causes COVID-19?
SARS-CoV-2
what does SARS stand for?
severe acute respiratory syndrome
what kind of genome does SARS-CoV-2 have?
where does that put it on the Baltimore classification system?
- ssRNA (+) genome
- group IV
what are the two receptors that SARS-CoV-2 binds to?
ACE2 and TMPRSS2
virulent phages ________ immediately upon entry. then, they _____ the bacterial host cell
multiply; lyse
what is a lysogenic relationship?
when a virus integrates its genome into the host’s genome so that whenever the host replicates it’s genome, the virus’ genome is replicated too (lysogenic cycle)
when it’s done doing that, it enters the lytic cycle (lysing of the cell)
what are some of the advantages of lysogeny?
- bacteria immune to superinfection
- phages may give bacteria beneficial genes
- viruses are ensured to survive in the presence of other phages
what does cytocidal infection of eukaryotic cells lead to?
death of the cell through lysis
if bacteria is grown in media, will the media increase or decrease in turbidity when infected with a virus?
decrease, because the virus will kill the bacteria
what is a PFU in a plaque assay?
- plaque-forming units
- 1 plaque = 1 virion = 1 PFU
- each individual phage its own plaque
if there is 10x less virus in a diluted solution, there will be _______ plaque
10x less plaque
what diseases do prions cause in humans and animals? what are some examples?
neuro-degenerative diseases
- Scrapie in sheep
- Bovine spongiform encephalopathy (mad cow disease)
- Kuru, Creutzfeld-Jakob disease
how do prions change proteins to cause disease?
cellular proteins are present in normal forms, but prions are present in abnormal forms. prions cause normal protein to change into abnormal proteins, and this cascades
