Virology Exam 1

Question 1

One enzyme that must be encoded by almost all viruses with RNA genomes is…

Answer 1

RNA polymerases using RNA as template

Question 2

minus strand of viral RNA is one in which

Answer 2

is complementary to mRNA

Question 3

who inserts viral proteins into a vesicle membrane

Answer 3

animal cells

Question 4

what type of virus genome that most resembles cellular mRNA

Answer 4

single strand, positive strand mRNA

Question 5

which type of animal virus can enter cell by receptor-mediated endocytosis

Answer 5

either enveloped or unenveloped viruses

Question 6

T7 phage DNA enters bacterial cell by mechanism involving

Answer 6

digestion of cell membrane by phage capsid proteins to allow only DNA to enter cell

Question 7

late genes in T7 are transcribed when

Answer 7

viral RNA polymerase protein is made

Question 8

phage RNA polymerase

Answer 8

makes primer for phage DNA replication

Question 9

phage DNA polymerase

Answer 9

synthesizes phage DNA

Question 10

host RNA polymerase

Answer 10

transcribes early phage genes

Question 11

what feature do T7, T even phages and mycobacterium have in common?

Answer 11

double stranded DNA genome

Question 12

which of the following promoters is blocked by cI protein

Answer 12

both PL and PR

Question 13

what is the function of cos sites in the lambda phage genome

Answer 13

circularize the genome

Question 14

virus replication cycle

Answer 14

• binding of receptor on cell
• entry and uncoating
• early gene expression
• replication of viral genome
• late gene expression
• assembly of visions
• exit cell

Question 15

icosahedral symmetry

Answer 15

• 20 faces
• 12 points
• fivefold, threefold and twofold rotational axes
• hexons and pentons
• may require scaffolding proteins

Question 16

virus envelopes

Answer 16

• lipid bilayer and viral glycoproteins

- obtained by budding

Question 17

most plant viruses and many viruses of vertebrates have what kind of genome

Answer 17

positive-strand RNA

Question 18

all viruses with negative-strand RNA genomes have what?

Answer 18

helical nucleocapsids and some have fragmented genomes

Question 19

viruses with double-stranded RNA genomes are characterized by what

Answer 19

fragmented genomes and capsids with icosahedral symmetry

Question 20

viruses with reverse transcription step can have what kind of genome

Answer 20

DNA or RNA

Question 21

name the 5 classifications

Answer 21

• dsDNA
• ssDNA
• dsRNA
• • ssRNA
• • ssRNA
• retrovirus + RNA

Question 22

dsDNA

Answer 22

• carries DNA-dependent RNA polymerase to produce mRNA

Question 23

ssDNA

Answer 23

• carries DNA-dependent DNA polymerase to create dsDNA

- carries DNA-dependent RNA polymerase to create mRNA from dsDNA

Question 24

dsRNA

Answer 24

• carries RNA-dependent RNA polymerase to create mRNA

Question 25

+ ssRNA

Answer 25

is the same thing as mRNA

Question 26

- ssRNA

Answer 26

- carries RNA-dependent RNA polymerase to create +RNA or mRNA

Question 27

retrovirus + RNA

Answer 27

- 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

Question 28

fusion proteins

Answer 28

proteins in cell wall that undergo major conformational changes that lead to fusion

Question 29

what triggers passage of virus from endosome to the cytosol

Answer 29

pH

Question 30

what microtubules move the visions an dcapsids within the cell

Answer 30

dyenin and dynactin

Question 31

how can virus entry be prevented?

Answer 31

- intercept virus before it reaches cell with neutralizing antibodies - flood extracellular space with soluble receptor - block cellular receptor - inhibit membrane fusion - inhibit uncoating

Question 32

entry of virus into a cell occurs by what mechanism?

Answer 32

- fusion - receptor-mediated endocytosis - passage of virion genome through a pore

Question 33

podovirus

Answer 33

has tail that is short

Question 34

myovirus

Answer 34

contains a contractile tail

Question 35

siphovirus

Answer 35

has long, flexible tail

Question 36

T7 virus/genome

Answer 36

- 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

Question 37

early genes

Answer 37

control expression of phage gene

Question 38

middle genes

Answer 38

control phage DNA replication

Question 39

late genes

Answer 39

code for structural proteins

Question 40

concatemers

Answer 40

- 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

Question 41

T7 entry into the cell

Answer 41

- DNA is injected by tail - DNA is spooled in by cellular RNA polymerase - DNA is spooled in by T7 RNA polymerase

Question 42

what is the one-step growth curve

Answer 42

how long it takes for virus to replicate and lyse the cell

Question 43

eclipse stage

Answer 43

phages in cell, but haven't been released

Question 44

latent stage

Answer 44

phages have been released from cell

Question 45

maturation stage

Answer 45

time to when you have first completely assembled phage until phages are first released

Question 46

lambda phage

Answer 46

- also referred to as temperate | - can be lytic or lysogenic

Question 47

prophage

Answer 47

bacterial DNA that contains integrated DNA from the phage

Question 48

virion of lambda phage

Answer 48

- head is naked icosahedral capsid (T=7) - flexible, tube shaped tail - terminal fibers

Question 49

lambda phage genome

Answer 49

- 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

Question 50

types of repressors

Answer 50

cro and cI

Question 51

cro

Answer 51

promotes lytic behavior | - suppresses cI synthesis and regulates early gene transcription

Question 52

cI

Answer 52

promotes lysogenic behavior | - blocks expression of lytic program by regulating PL, PR and PRM

Question 53

operator

Answer 53

site at which the repressor binds

Question 54

PRM

Answer 54

maintains transcription of cI

Question 55

PR

Answer 55

maintains transcription of cro

Question 56

induction

Answer 56

- leads to lytic replication | - cleavage of cI repressor in cells with damaged DNA lead to this

Question 57

lambda DNA replication

Answer 57

- 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