Virology

Question 1

what is a virus?

Answer 1

obligate intracellular pathogens

Question 2

can viruses replicate anywhere? Why?

Answer 2

no, they must replicate inside a host living cells, by using the host’s cellular machinery to do transcription, translation and replication

Question 3

what do viruses synthesize?

Answer 3

virions

Question 4

what do virions do?

Answer 4

they help in the transfer of the viral genome (RNA or DNA) to other living cells

Question 5

what do viruses lack?

Answer 5

mitochondria, ribosomes, enzymes

Question 6

true or false: viruses are bigger than bacteria and host cells

Answer 6

false, they are much more smaller

Question 7

what are the 2 stages of a virus?

Answer 7

1) Virion = the infectious form
2) intracellular form (its genome alone) = non-infectious

Question 8

what is the structural parts of a virus (after infection)?

which of these parts is optional?

Answer 8

1) Viral DNA/RNA
2) nucleocapsid
3) matrix tegument
4) envelope

the ENVELOPE is optional

Question 9

what are the 3 forms that the nucleocapsid can have?

Answer 9

1) icosahedral
2) helical
3) complex

Question 10

how do we find the viral envelope? (how does it look or what is it?)

Answer 10

its the host cell lipid bilayer, with viral glycolipids in the surface

Question 11

how do you know if the virus is enveloped or naked?

Answer 11

enveloped = nucleocapsid + glycoproteins and the nuclear membrane

naked = only the nucleocapsid

Question 12

what makes up the nucleocapsid?

Answer 12

1) DNA/RNA
2) structural protein

Question 13

what determines what steps and enzymes are necessary to create the viral mRNA?

Answer 13

the type of nucleic acid

Question 14

what enzyme is important for single stranded RNA retrovirus?

Answer 14

reverese transcription

Question 15

why is it very important to know what type of nucleic acid a virus is?

Answer 15

because by determining what type of nucleic acid the virus is, we can select the corret anti-biotic to treat it with

Question 16

what type of nucleocapsid do all naked virus have?

Answer 16

icosahedral

Question 17

what type of nucleocapsid do all enveloped viruses have?

Answer 17

complex

Question 18

what is the function of the outer structural proteins?

Answer 18

1) protect the genetic material
2) mediates the attachment of the virus to specific host cell receptors on the cell surface
3) activate the immune system to kill virus cell (activate neutralizing antibodies and CTL’s)

Question 19

when does a immune response occur? (after what 2 events?)

Answer 19

1) natural exposure
2) immunization

Question 20

what determines the viral classification?

Answer 20

nucleic acid and the envelope

Question 21

what viruses are less stable?

Answer 21

enveloped DNA/RNA viruses

Question 22

how are enveloped DNA/RNA viruses transmitted?

Answer 22

through direct contact

(blood or bodily fluids)

Question 23

what viruses are more stable and can survive a long time in the environment?

Answer 23

naked DNA/RNA viruses

Question 24

how do naked viruses spread?

Answer 24

through indirect means (fecal-oral route)

Question 25

what is an example of an enveloped DNA virus?

Answer 25

Hep. B

Question 26

what is an example of a naked RNA virus?

Answer 26

Hep A

Question 27

What are the DNA viruses?

Answer 27

1) Parvovirus 2) Papillomaviridae 3) Polyomaviridae 4) Adenovirus 5) Herpes virus 6) Hepadnavirus 7) Poxvirus

Question 28

what 2 viruses have polymerase?

Answer 28

1) Hepadnavirus 2) Poxvirus

Question 29

All DNA viruses are icosahedral, except for?

Answer 29

Poxvirus

Question 30

all DNA viruses are what single straded or double stranded? Who is the exception?

Answer 30

double stranded DNA Parvovirus

Question 31

what is a double stranded RNA virus example?

Answer 31

Reovirus

Question 32

what are the positive RNA viruses?

Answer 32

1) Calicivirus 2) Picorna 3) Flavivirus 4) Togavirus 5) Coronavirus 6) Retrovirus

Question 33

what is an example of a retrovirus?

Answer 33

HIV

Question 34

what are the 6 types of negative RNA viruses?

Answer 34

1) Paramyxovirus 2) Rhabdovirus 3) Filovirus 4) Orthomyxovirus 5) Bunyavirus 6) Arenavirus

Question 35

what are the 5 steps of the viral cycle?

Answer 35

1) attachment 2) penetration 3) synthesys 4) assembly 5) release

Question 36

what is PFU?

Answer 36

is a plaque forming unit once virus infects a single cell, spread and kill surrounding cells to cause a plaque (a clear area or dead cells) surrounded by live cells.

Question 37

What is it called the time after the nucleic acid is released and before the virus starts replicating?

Answer 37

eclipse phase

Question 38

the time before full virions are released after infection is called?

Answer 38

the latent phase

Question 39

what do virions have that allows them to restrict the host cell specificity (or tropism)?

Answer 39

VAP ( virion attachment protein)

Question 40

what are the VAP of the HIV virus? to what do they attach to?

Answer 40

GP 120---binds to CCR5 on macrophages GP140 ----binds to CD4

Question 41

what cells does HIV infect?

Answer 41

CD4 cells

Question 42

what are the VAP of epstein-Bar virus? to what receptor do they bind? and on what cell?

Answer 42

CR2 and CD21 they bind to C3d complement receptor on B cells

Question 43

to what does rhinovirus VAP bind to ? on what cells?

Answer 43

ICAM-1 on endothelial cells

Question 44

what is the VAP of Influenza A virus? to what cells does it bind to?

Answer 44

sialic acid and binds to epithelial cells

Question 45

where does penetration of a virus occur?

Answer 45

at the cell surface

Question 46

where does uncoating occur in a virus?

Answer 46

once inside the cell

Question 47

the process of uncoating is dependant on what?

Answer 47

it is pH dependant

Question 48

in order for the virus to replicate, what must physically separate in the viral structure?

Answer 48

the capsid from the viral genome

Question 49

uncoating depends on what in the host cell?

Answer 49

depends on cellular enzymes

Question 50

if the virus loses this from its structure during uncoating will lead to loss of ability to infect other cells...

Answer 50

structural proteins

Question 51

what mechanisms are used to facilitate nucleic acid release?

Answer 51

1) clathrin-dependent pathway 2) macropinocytosis 3) caveolar pathway 4) clathrin- and cavolin-independant pathway 5) phagocytosis

Question 52

the virion genome will encode this two types of genes:

Answer 52

early gene late gene

Question 53

what is the early gene made by the viral genome used for?

Answer 53

it is needed for replication

Question 54

what is the late gene made from the viral genome used for?

Answer 54

it is required for packaging

Question 55

what kind of proteins does the viral genome instruct the cell to produce?

Answer 55

structural and non-structural proteins

Question 56

what are structural proteins?

Answer 56

are the late proteins found in virion particles

Question 57

what are non-structural proteins?

Answer 57

early proteins produced in infected cells but not found in virions

Question 58

what does the herpes virus have to do before it can integrate into the host genome?

Answer 58

it has to use reverse transcriptase to convert RNA --\> DNA

Question 59

what enzyme does the herpes virus use to integrate into the host genome?

Answer 59

integrase

Question 60

what happens in the assembly phase of a virus?

Answer 60

viral proteins and copies of nucleic acid are assembled

Question 61

how are the virions assembled during the assembly phase?

Answer 61

virions are formed by packaging the genomes with capsid proteins and if the virus is enveloped, by wrapping the nucleocapsid in an envelope

Question 62

how are non-enveloped viruses released into the body once they get made in the infected cell?

Answer 62

when the cell dies, they get released

Question 63

how are enveloped virions released into from the cell they got made?

Answer 63

by exocytosis

Question 64

where do enveloped viruses acquire their lipid membrane?

Answer 64

at the cellular plasma membrane or at the golgi by budding

Question 65

what happens to the plasma membrane while the virus used budding?

Answer 65

virus takes a piece of the plasma membrane and pulling away a piece and eventually reducing the amount on the cell