Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

VIrology > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

What challenges does a virus face in order to replicate?

A
  1. Must find the correct host
  2. Must be able to get into the host (counter barriers at cell surface)
  3. Must be able to find correct cell
  4. Must be able to enter cell
  5. Must be able to take over host cell machinery
    To replicate genome, produce proteins, assemble
  6. Must be able to evade the immune response
  7. Must successfully leave the cell and enter neighboring cells
  8. Not kill the host too quickly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the 6 steps to virus replication?

A
  1. Attachment
  2. Entry
  3. Replication of genome and protein production
  4. Virus regulation of cellular activities
  5. Assembly
  6. Release
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what happens during attachment?

A
  • Virus moieties interact with the cell surface

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

during attachment Virus surface proteins ________ bind to cell surface molecules called _______, not always a protein

A

glycoproteins, receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Ensure the virus gets into the correct host cell is called?

A

cell tropism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Influenza virus cell tropism appears to be controlled by the linkage between ____-____ and ________on the cell surface

A

sialic acid and ___________

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

_____ are a ‘mixing vessel’ for influenza as they have both α 2,3 and α 2,6 linked sialic acids

A

pigs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

influenza virus has a surface protein that detaches the virus from inappropriately bound non-cellular sugars __________

A

(neuraminidase)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

cell receptors for viruses includes both ______ and ________

A

proteins and sugars

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Multi-stage binding process ensures fidelity of cellular________

A

tropism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

the herpes simplex virus is _______ cell tropism

A

promiscuous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

epstein bar virus is _____ cell tropism

A

restricted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

describe entry with enveloped virus

A

fusion with the surface membrane or endosomal membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

describe entry with non enveloped virus

A

particle internalized by the cell, crosses membrane by lysis or permeabilization

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

describe entry into a vacuole (3 steps)

A
  1. clathrin mediated endocytosis
  2. calveolae mediated endocytosis
  3. macropinocytosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

calveolae

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

describe macropinocytosis

A
  • virus coated with phosphatidylserine stimulates cell to make lamelipodia
  • large vessicle clalled macropinosomes form
  • carry virus into the cell and fuse with an endosome
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

when the capsid enters the cytosol acidification can cause …

A
  1. change in envelope structure and capsid is released into cytosol
  2. change in conformation of capsid proteins altered virion enters cytosol or genome eneters cytosol
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

function of amantadine

A
  • Binds to the inside of the M2 ion channel, blocking its ability to pump protons
  • Resistance developed with changes in amino acids lining the M2 channel (drug can’t bind)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

replication has 3 phases

A
  1. eclipse phase
    - Right after virus entry there is a period of time where no infectious particles can be detected in the infected cell
  2. log phase
    - phase infectious particles are being released, cell taken over by virus
  3. cell death
    - In many cases the culmination of a virus infection
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what are some sites for virus replication

A
  1. Most DNA viruses and some RNA viruses replicate in the nucleus
  2. Most RNA viruses replicate in the cytoplasm
  3. Large DNA viruses set up “second nucleus” in the cytoplasm and replicate there
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how does a virus enter the nucleus

A
  1. viral proteins have nuclear localization signals
  2. Small size to enter through the nuclear pore intact
  3. Disassemble into subunits
  4. Enter the nucleus during cell division when nuclear envelope is dissolved
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

*cell tropism

A

all of the above

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

*which virus has a promiscuous cell tropism?

A

herpes simplex virus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

*how does an enveloped virus enter a cell?

A

fusion with the cell membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

*How does influenza virus use acidification of the endosome to enable entry?

A

changes HA molecule to allow fusion of viral envelope with the endosomal membrane

27
Q

synthesis of viral proteins must occur in the ________

A

cytoplasm

28
Q

Viruses that replicate their genomes in the nucleus must export viral mRNAs to the cytoplasm for ___________

A

translation

29
Q

In general,________proteins are made prior to structural proteins

A

non structural

30
Q

DNA synthesis is catalyzed by ______-_______

A

dna polymerase

31
Q

DNA is made in a __________ direction

A

5’ to 3’

32
Q

issues faced by viruses include

A
  1. Manipulation of the host cell machinery to replicate the genome
  2. Replication of unique genomic material
  3. Appropriate use of cellular resources for high levels of replication
33
Q

what is the first strategy to obtain machinery to replicate the genome?

A
  • induce the cell to enter S phase

- Makes a protein, large T antigen, that interacts with host Rb, blocks its function and drives the cell into S phase

34
Q

what is the second strategy to obtain machinery to replicate the genome?

A
  • replication machinery is encoded by the virus

- RNA viruses encode for their own RNA dependent RNA polymerase

35
Q

describe viruses with dsDNA genomes

A
  • Often large viruses with complex virions
  • Produce many virus-specific enzymes and proteins for replication
  • Replication in nucleus
  • rolling circle replication
36
Q

describe viruses with ssDNA genomes

A
  • Very small genomes (1759 – 11,000 bp) ex: Parvoviridae
  • Does not have the ability to turn on cellular DNA synthesis
  • Replication in the nucleus
37
Q

Hepadnaviridae

A

Hepatitis B virus is the only virus with this genome type that infects humans

38
Q

DNA viruses that use RNA intermediates include

A
  • hep B
  • Genome is a partially dsDNA genome
  • Reverse transcriptase and primers are covalently attached to the genomic DNA
39
Q

Why doesn’t Hepadnaviridae use the host cell’s DNA polymerase?

A
  • It would have to infect only actively dividing cells, induce cell cycle etc.
    (Instead, it uses a reverse transcriptase that has DNA polymerase activity too)
  • Its reverse transcriptase is a low fidelity polymerase
    (It will introduce errors that may produce mutants with an evolutionary advantage)
40
Q

describe RNA syntheis

A
  • Uses ribonucleic acids instead of deoxyribonucleic acids
  • Synthesis occurs in a 5’ to 3’ direction
  • RNA polymerase does not require a primer
41
Q

what are the types of RNA genomes?

A
  • Single-stranded RNA genomes (positive sense, negative sense, ambisense)
  • double stranded RNA genomes
  • segmented genomes
  • RNA genome with DNA intermediate
42
Q

Problems with RNA genomes:

A
  1. RNA less stable than DNA (especially ssRNA)
    Gets degraded by nucleases in the cell
  2. Cell does not have an RNA dependent RNA polymerase
  3. RNA polymerases are notoriously low fidelity enzymes
43
Q

(+) ssRNA genomes are infectious (T F)

A

true

44
Q

poliovirus replication makes more (+) then (-) (T F)

A

true

45
Q

poliovirus replication is associated with the _____ _____

A

smooth ER

46
Q

describe viruses with (-) ssRNA genomes

A
  • Genome is not infectious, cannot be translated directly, therefore virus must package RNA polymerase in particle
  • Once in the cell, both mRNA and genomic copies are made
47
Q

Viruses with (+) ssRNA genomes that use a DNA intermediate are integrated into hist DNA as _________

A

provirus

48
Q

HIV can ________- cells

A

transform

49
Q

what are the 2 possible mechanisms for HIV to transform cells:

A
  • Integration of genome affects adjacent cell cycle controlling genes disrupting (or enhancing) their function
  • Expression of viral oncogenes
50
Q

describe ambisense genomes

A
  • Replicate similarly to (-) ssRNA viruses in that they package an RNA dep RNA polymerase in their particles
  • Rather than have a genome that can be directly translated
51
Q

*Small DNA viruses replicate their genomes:

A

in the nucleus

52
Q

*How does a virus get its genome into the nucleus?

A

all of the above

  1. Small enough to transport whole virion through the nuclear pore
  2. Bind to nuclear pore and inject genome through and into nucleus
  3. Genome alone enters nucleus through pore
  4. Enter nucleus during mitosis and nuclear envelope degradation
53
Q

*Which of the following describes the temporal regulation of HSV-1 replication?

A

all of the above

54
Q

viral regulation of cellular activities involves what strategies:

A
  • Drive cell into S phase in order to access resources for replication
  • Disrupt cellular metabolism to alter activity of transcription factors
  • Transfer of caps from cellular to viral mRNAs
55
Q

Influenza virus doesn’t make it’s own 5’ cap (T F)

A

T

56
Q

segmented (-)ssRNA influenza virus occurs in the _______

A

nucleus

57
Q

what are the two hypothesis for segmented genome localization

A
  1. There is active sorting of the genome segments to ensure that a full set is incorporated into a forming virus particle
  2. RNAs are encapsidated at random, and only those with a full set of segments are infectious
58
Q

simple virus assembly includes:

A
  • VP1-4 (capsomers) assemble into pentamers
  • Fifth protein, vpg, associates with RNA genome
  • Genome is either
    1. Inserted into preformed capsid
    2. Condenses with the proteins during capsid formation
59
Q

comple virus assembly includes:

A
  • Icosahedral capsid but larger genome and more complex structure
  • Uses scaffolding proteins
  • Proteins required for assembly but not included in the infectious particle
60
Q

virus release includes:

A
  1. cell lysis

2. budding

61
Q

cell lysis involves:

A
  1. Viroporin: (Adenoviridae, Picornaviridae) encode proteins late in infection that disrupt the cell membrane
  2. Lytic phospholipids: (Phycodnaviridae: infects algae) virus may induce the synthesis of lytic phospholipids
  3. Lysozymes: (prokaryotic viruses) encode lysozymes that digest the cell wall, causing lysis by osmotic shock
    * non enveloped some enveloped
62
Q

*What polymerase do ssDNA viruses use to copy their genomes?

A

Host-encoded DNA dependent RNA polymerase

63
Q

Which virus genome would be considered infectious?

A

+ ssRNA

64
Q

*What phospholipid bilayer is used by viruses for their envelope?

A

all of the above

  1. Plasma membrane
  2. Nuclear membrane
  3. ER membrane
  4. Golgi membrane
  5. All of the above

VIrology (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions