Virology Exam 1 Flashcards
One enzyme that must be encoded by almost all viruses with RNA genomes is…
RNA polymerases using RNA as template
minus strand of viral RNA is one in which
is complementary to mRNA
who inserts viral proteins into a vesicle membrane
animal cells
what type of virus genome that most resembles cellular mRNA
single strand, positive strand mRNA
which type of animal virus can enter cell by receptor-mediated endocytosis
either enveloped or unenveloped viruses
T7 phage DNA enters bacterial cell by mechanism involving
digestion of cell membrane by phage capsid proteins to allow only DNA to enter cell
late genes in T7 are transcribed when
viral RNA polymerase protein is made
phage RNA polymerase
makes primer for phage DNA replication
phage DNA polymerase
synthesizes phage DNA
host RNA polymerase
transcribes early phage genes
what feature do T7, T even phages and mycobacterium have in common?
double stranded DNA genome
which of the following promoters is blocked by cI protein
both PL and PR
what is the function of cos sites in the lambda phage genome
circularize the genome
virus replication cycle
- binding of receptor on cell
- entry and uncoating
- early gene expression
- replication of viral genome
- late gene expression
- assembly of visions
- exit cell
icosahedral symmetry
- 20 faces
- 12 points
- fivefold, threefold and twofold rotational axes
- hexons and pentons
- may require scaffolding proteins
virus envelopes
- lipid bilayer and viral glycoproteins
- obtained by budding
most plant viruses and many viruses of vertebrates have what kind of genome
positive-strand RNA
all viruses with negative-strand RNA genomes have what?
helical nucleocapsids and some have fragmented genomes
viruses with double-stranded RNA genomes are characterized by what
fragmented genomes and capsids with icosahedral symmetry
viruses with reverse transcription step can have what kind of genome
DNA or RNA
name the 5 classifications
- dsDNA
- ssDNA
- dsRNA
- ssRNA
- ssRNA
- retrovirus + RNA
dsDNA
- carries DNA-dependent RNA polymerase to produce mRNA
ssDNA
- carries DNA-dependent DNA polymerase to create dsDNA
- carries DNA-dependent RNA polymerase to create mRNA from dsDNA
dsRNA
- carries RNA-dependent RNA polymerase to create mRNA
+ ssRNA
is the same thing as mRNA
- ssRNA
- carries RNA-dependent RNA polymerase to create +RNA or mRNA
retrovirus + RNA
- reverse transcription with RNA-dependent DNA polymerase to create ssDNA
- uses DNA polymerase to create dsDNA
- integrates into the cells DNA
- then creates mRNA from the cells DNA
fusion proteins
proteins in cell wall that undergo major conformational changes that lead to fusion
what triggers passage of virus from endosome to the cytosol
pH
what microtubules move the visions an dcapsids within the cell
dyenin and dynactin
how can virus entry be prevented?
- intercept virus before it reaches cell with neutralizing antibodies
- flood extracellular space with soluble receptor
- block cellular receptor
- inhibit membrane fusion
- inhibit uncoating
entry of virus into a cell occurs by what mechanism?
- fusion
- receptor-mediated endocytosis
- passage of virion genome through a pore
podovirus
has tail that is short
myovirus
contains a contractile tail
siphovirus
has long, flexible tail
T7 virus/genome
- linear dsDNA
- terminal direct repeated sequence
- early, middle and late genes
- RNA polymerase immediately begins transcribing as the DNA enters cell
- makes own polymerase
- concatemers
- can ONLY BE LYTIC
early genes
control expression of phage gene
middle genes
control phage DNA replication
late genes
code for structural proteins
concatemers
- terminal repeated sequence in T7 genomes
- solves problem of losing sequences at end of DNA during replication
- only 1 genome fills a head, or one concatemer
T7 entry into the cell
- DNA is injected by tail
- DNA is spooled in by cellular RNA polymerase
- DNA is spooled in by T7 RNA polymerase
what is the one-step growth curve
how long it takes for virus to replicate and lyse the cell
eclipse stage
phages in cell, but haven’t been released
latent stage
phages have been released from cell
maturation stage
time to when you have first completely assembled phage until phages are first released
lambda phage
- also referred to as temperate
- can be lytic or lysogenic
prophage
bacterial DNA that contains integrated DNA from the phage
virion of lambda phage
- head is naked icosahedral capsid (T=7)
- flexible, tube shaped tail
- terminal fibers
lambda phage genome
- linear dsDNA but circulizes once in the cell
- ends are cohesive-sticky ends (cos sequences)
- codes for 60 proteins
- transcribed by cellular RNA polymerase
- genes grouped by function
- immediate early, early and late genes
- repressors, antiterminators and activators present
types of repressors
cro and cI
cro
promotes lytic behavior
- suppresses cI synthesis and regulates early gene transcription
cI
promotes lysogenic behavior
- blocks expression of lytic program by regulating PL, PR and PRM
operator
site at which the repressor binds
PRM
maintains transcription of cI
PR
maintains transcription of cro
induction
- leads to lytic replication
- cleavage of cI repressor in cells with damaged DNA lead to this
lambda DNA replication
- rolls circular DNA into concatemer with cos sites
- cos sites are where the cutting sites are (by terminus), only one cos site to cos site goes into a virus
