Virology

Front 1

do viruses have their own metabolic system

Back 1

no.

they infect the host cell and take over the host cell machinery in order to replicate and reproduce.

Front 2

name some general characteristics of viruses

Back 2

1)viruses contain no ADP, ATP, or sugars

2)they must reproduce inside a host cell

3) can infect only a limited # of cell types

4) infect every type of cell

5) are protected from most of hosts immune

6) contain either DNA or RNA

Front 3

name some differences between viruses and pathogens

Back 3

1) viruses are acellular

2) the reproduce via an assembly process

3) all viruses are haploid (except retroviruses)

4) they contain either DNA or RNA

5) they lack organelles, cytoplasm, nucleus

Front 4

what is a capsid

Back 4

circular protein coat made up of very small protein subunits (called capsomeres) that protect the virus core.

* symmetrically spontaneously self assembles therefore does not need an enzyme.

Front 5

what is an envelope

Back 5

made of host cell membrane & glycoproteins from the viral host. it is more common in animal viruses. protects the virus core

*Note: it is maintained only in aqueous environments, and cannot survive the harsh GI tract

Front 6

structure of a naked helical viruses

Back 6

rigid structure, cylindrical image.

Front 7

structure of an isohedral nucleocapsid

Back 7

20 sided with 12 evenly spaced corners. may have one or multiple capsomers.

Front 8

viral envelope proteins function

Back 8

functionally provide host cell recognition & binding to host cell upon infection

Front 9

what is a nucleocapsid

Back 9

capsid + genome

Front 10

definition of mutation

Back 10

change in nucleotides within a single genome

Front 11

define strain

Back 11

same virus but isolated from different patients or geographical locations

Front 12

define type

Back 12

same virus but responding differently to antibody detection (sterotypes)

Front 13

define variant

Back 13

virus whore phenotype differs from wild type

Front 14

compare RNA and DNA rates of mutation

Back 14

DNA rates of mutations = 1 in every 10(-9)

RNA rates of mutations = 1 in every 10(-3)

* RNA viruses have a higher rate of mutation, since RNA-dependednt RNA polymerases are typically more error prone than DNA-dependent DNA polymerases

Front 15

do viral RNA polymerases have proofreading capabilities

Back 15

NO

Front 16

all RNA viruses encode an RNA-dependednt RNA Polymerase except?

Back 16

Retroviruses, which encode via Reverse Transcriptase.

Front 17

recombination

Back 17

genetic information is exchanged between two distinct genomes

done via: 1)strand brokerage and re-ligation (occurs mostly in DNA) or 2) copy choice (occurs only in RNA)

Front 18

reassortment

Back 18

the exchange of genetic material between 2 segmented genomes

* commonly seen in strains of Influenza A virus

Front 19

list the steps of viral replication

Back 19

1) recognition of host cell

2) attachment

3) penetration

4) uncoating

5) synthesis of nucleic acids & proteins

6) assembly

7) release from host cell

Front 20

define tropism

Back 20

protein-protein affinity for a specific cell type

Front 21

attachment of naked viruses

Back 21

direct interaction between capsid (ligand) and host cell receptor

ex: rhinovirus & ICAM1

* sometimes the groove is too small for the antibody to enter making it difficult to cure the common cold

Front 22

attachment of enveloped viruses

Back 22

the viral envelope contains spikes, these spikes act as a ligand for interaction with the host cell receptor.

Front 23

penetration of naked viruses

Back 23

1)direct penetration - only the genetic material enters the host cell while the capsid remains extracelluluar

2) Endocytosis - internalization of clatherin-coated or caveolin coated pits into cell membrane

Front 24

penetration of enveloped viruses

Back 24

1) fusion - the nucleic capsid enters the host

2) endocystosis - internalization of clatherin-coated or caveolin coated pits into cell membrane

Front 25

uncoating

Back 25

the removal of capsid to expose viral genome to the inside of the host cell.

this is the final step in early phase pf viral replication

Front 26

where does DNA genome replication occur?

name an exception.

Back 26

1)in the nucleus

2) the poxvirus - is so large that it carries its own enzymes. therefore it can replicate in the cytosol and doesn't need to go into the nucleus.

Front 27

where does RNA genome replication occur?

Back 27

1)occurs in the cytoplasm

2) retroviruses - use reverse transcriptase

Front 28

define inclusion bodies

Back 28

compact masses of viruses that may be present in the nucleus of cytoplasm of the host cell they can be identified by light microscopy.

Front 29

describe the difference between assembly of a isohedral capsomer vs a helical virus.

Back 29

1) isohedral capsomeres - spontaneously assemble into an empty capsid that includes a packaging sequence.

2) Helical virons - utilize the genomic material as a starting point for assembly. this genome includes a pac site to which the capsomer subunit bind.

Front 30

describe maturation

Back 30

once inside the capsid, changes take place. most commonly they process a protein precursor into the final product.

* if these changes are not made, the vision will not be infectious.

Front 31

describe release of naked viruses

Back 31

1) Cell Lysis - occurs due to viral overload

2) Exocytosis - similar to budding, however viruses do NOT acquire a portion of the membrane.

Front 32

describe release of enveloped viruses

Back 32

1) Budding - assembled virions distend through a membrane. the irons incorporate part of the host cell as it exits.

2) Exocytosis - similar to budding, however viruses do NOT acquire a portion of the membrane.

Front 33

describe the difference between a permissive and non-permissive cell

Back 33

once a virus infects a host, if the cell is a non-permissive cell (i.e it lacks appropriate cell receptors) no infection will occur.

Front 34

describe an Abortive infection

Back 34

the iron enters the cell but does not proceed through all the steps of the replication cycle (failed infection)

Front 35

describe an Acute/Lytic Infection

Back 35

rapid onset, period of disease, followed by clearenace of the virus. often result in death of the host cell via lysis

Front 36

describe a Persistent Infection

Back 36

virus that lingers and is not readily cleared by the immune system. in these infections the host survives, harboring the virus. it can be broken down into: chronic infection, latent infection, or transforming,

Front 37

describe a Chronic Infection

Back 37

can be lifelong, continuous production and shedding of virions.

ex: hep B & C

Front 38

describe a Latent Infection

Back 38

intermittent periods of viral replication and shedding with long periods of dormancy when the virus is not replicating.

ex: herpes simple & varicella-zoster (chicken pox)

* can not be targeted therefore can't be killed.

Front 39

Describe a Recurrent Infection

Back 39

virus cleared but may catch again

ex: common cold

Front 40

describe a Transforming Infection

Back 40

the virus causes the host cell to lose growth control resulting in tumor formation

Ex: HTLV