Test 3-6 (Medical Viro)

Question 1

What is a virus?

Answer 1

-acellular infectious agent
-a nucleic acid surrounded by a protein coat
-obligate parasite (need to live in another organism) = -Do not carry out metabolism & -Lack organelles and ribosomes.
-20 – 300 nm in size

Question 2

virus genomes

Answer 2

-contiguous (one long strand) or segmented (need each part)
-DNA or RNA
-single (+ sense=correct orientation for protein synthesis); - sense = not in correct order.. .ribosome cant read strand) or double stranded

Question 3

matrix/tegument of virus

Answer 3

-in envelope surrounded viruses
-between capsid and envelope
-needed to jump start viral life cycle

Question 4

viral attachment proteins are used for and found on

Answer 4

-on envelope or capsid in no enveope
-needed for attachment durp

Question 5

ssDNA virus family

Answer 5

1) parvoviridae family

Question 6

dsDNA virus family

Answer 6

1) papovaviridae family
2) adenoviridae family
3) herpesviridae family
4) poxviridae family
5) hepadnaviridae

Question 7

dsRNA virus family

Answer 7

1) reoviridae family

Question 8

-ssRNA virus family

Answer 8

1) orthomyxoviridae family
2) Paramyxoviridae fam
3) Rhabdoviridae family
4) Bunyaviridae family
5) Arenaviridae family
6) Filoviridae family

Question 9

+ssRNA

Answer 9

1) Togaviridae family
2) Flaviviridae family
3) Coronaviridae family
4) Retroviridae family
5) Picornaviridae family
6) Caliciviridae family
7) Hepeviridae family

Question 10

Properties of RNA viruses

Answer 10

-RNA is labile and transient.
-Most RNA viruses replicate in the cytoplasm.
-Cells cannot replicate RNA. RNA viruses must encode an RNA-dependent RNA polymerase.
-RNA viruses, except (+) RNA genome, must carry polymerases.
-RNA viruses are prone to mutation.

Question 11

capsid types

Answer 11

helical
icosahedral
complex

Question 12

naked capsid properties

Answer 12

-Are environmentally stable to the following:
Temperature;Acid;Proteases;Detergents;Drying
-Released from cell by lysis
(PROTEIN OUTERMOST SHELL)

Question 13

naked capsid viruses consequences of the properties

Answer 13

-Spread easily e.g., on fomites, from hand to hand, by dust, by small droplets
-Dry out and retain infectivity
-Survive the adverse conditions of the gut
-Resistant to detergents and poor sewage treatment

Question 14

envelope viruses properties

Answer 14

-Are environmentally labile, disrupted by the following: Acid;Detergents;Drying;Heat
-Modifies cell membrane during replication
-Are released by budding and cell lysis
(LIPID LAYER OUTER MOST)

Question 15

envelope viruses consequences of the properties

Answer 15

-Must stay wet
-Cannot survive the gastrointestinal tract
-Spreads in large droplets, secretions, organ transplants, and blood transfusions
-Does not need to kill the cell to spread

Question 16

VIrus life cycle summary

Answer 16

1. attachment
2. entry
3. mRNA production
4. protein and genome synthesis
5. Viron assembly
6. Egress

Question 17

Attachment and entry phase

Answer 17

-binds plasma membrane receptor –> direct fusion of membranes
-binds receptors –> triggers engulfment of virus with cell plsama membrane (vessicle) –> virus released into cell
-(acidification of vessicle for completion prior to release
-non enveloped do same thing – instead of fusion they just lyse the vessicle

Question 18

mRNA production phase

Answer 18

–>dsDNA - just use cells RNA pol
–>ssDNA - use cells DNA repair enzymes to make dsDNA then use cells RNA pol
–>+ssRNA (retrovirus)- rev transcriptase to make dsDNA then use cells RNA pol
–> +ssRNA (others) - dont need to do anything just make mRNA from their +ssRNA strand
–> –ssRNA - produce their own viral RNA dependent pol which uses their neg sense molecule to make mRNA
–>dsRNA - use viral RNA dep pol

Question 19

biggest challenge for DNA viruses?

Answer 19

cellular DNA rep machinery s not avail at all times

Question 20

different ways DNA viruses make cellular DNA rep machinery available

Answer 20

-SOLUTION 1: Make cellular DNA replication machinery available. Papovaviruses stimulate cell growth and DNA synthesis.
-SOLUTION 2: Encode viral proteins to synthesis genome. Poxviruses encode their own polymerase and enzymes to provide deoxyribonucleotides for DNA synthesis, replication machinery, and transcription machinery in the cytoplasm.

Question 21

biggest challenge for RNA viruses?

Answer 21

no cellular RNA-dependent RNA polymerase (RdRp)

Question 22

different ways RNA viruses make cellular DNA rep machinery available

Answer 22

-Solution 1- FOR +ssRNA viruses = encode a RdRp in genome, then since its + strand RNA the cells ribosomes will recognize your strand and make more RdRp which can make copies of genome
-Solution 2- FOR -ssRNA viruses = encode a RdRp in genome and carry the enzyme in your viron. your RdRp will work to make +ssRNA whcih is then recognized by cells ribsomes = more RdRP = more genome copies

Question 23

viron assembly phase

Answer 23

1) Individual viral proteins form into capsid subunits
2) Subunits combine to form complete capsid.
3) Viral genome and other essential virion components are selectively packaged into capsids.
4) Envelope is acquired. (only for enveloped viruses)
5) Virus exits cell.
6) Virions mature. (only for certain viruses)

Question 24

egress phase

Answer 24

1) budding - assembly same time as budding - a) cell plasma membrane modified to contain virus surface proteins. b) throw in whatever proteins if needed and genome c) pinch off from cell
2) lysis - cell died. Everything is assembled in house until ready to pop or cell cant hold anymore=pop

Question 25

changing viral genetic

Answer 25

1) point mutations - slow way
2) recombination - swapping genetic info between viral strands ONLY FOR DNA VIRUS
3) reassortment - FOR SEGMENTED VIRUS - mixing all segments (if both infect same cell) then daughter virus may have mixes of each virus that entered cell

Question 26

viral infection types

Answer 26

1) acute - immune system is able to fight all of it offex) common cold
2) latent with reactivation - immune system figths it off but the virus is able to hide and reactivate ex) HSV
3) chronic - low level continuous replication - ex) HepB

Question 27

invasion

Answer 27

1) oral transmission - contaminated food, saliva
2) conjunctiva
3) direct skin contact
4) tarns placental
5) sexual transmission
6) droplet transmission - inhalation
7) direct inoculation - injections, trauma, bites

Question 28

plaque assay

Answer 28

1) make single layer of healthy cells
2) add virus so single virus infects singles cells at different regions on plate
3) watch spread and “clearing” on plate as cells die (cytopathic effect)

PROVES VIRUS IS INFECTIOUS AND REPLICATING

Question 29

virus culture/plaque assays detect

Answer 29

infectous virons

Question 30

ELISA detects

Answer 30

viral antigens and glycoproteins

Question 31

ELISA and Western Blot detect

Answer 31

antibodies against virus

Question 32

virus culture/plaque assay advantages and limits:

Answer 32

-Positivity shows active viral infection.
-Restricted to viruses that replicate in tissue culture and produce cytopathic effect.

Question 33

electron microscopy detects

Answer 33

virion particles

Question 34

electron microscopy adv and limits

Answer 34

-Especially helpful in the identification of emerging viruses.
-Relatively expensive and technically challenging.– usually only done if there is some serious outbreak by the CDC or whoever

Question 35

(antigen detection) ELISA adv and limits

Answer 35

-Sensitive and quick.
-Requires specific antibody

Question 36

Polymerase Chain Reaction (PCR) detects

Answer 36

DNA genomes

Question 37

Polymerase Chain Reaction (PCR) adv and limits

Answer 37

-Highly Sensitive
-DNA sequence information must be available.

Question 38

Reverse transcriptase-Polymerase Chain Reaction(RT-PCR) detects:

Answer 38

RNA genomes

Question 39

Reverse transcriptase-Polymerase Chain Reaction (RT-PCR) adv and limts

Answer 39

-Highly Sensitive
-RNA sequence information must be available.

Question 40

Western Blot (serology) detects

Answer 40

Anti-viral Antibodies

Question 41

Western Blot (serology) adv and limits

Answer 41

-Sensitive and quick.
-Time must be allowed for the initiation of the immune response. Care must be taken to differentiate present from past infections.