Viruses Acellular Pathogens

Question 1

Define Virus

Answer 1

genetic element that cannot replicate independently of a living ( host) cell

Question 2

Define virology

Answer 2

study of viruses

Question 3

Define virus particle

Answer 3

• extracellular form of virus

- facilitates transmission from 1 host to another

Question 4

Define virion

Answer 4

infectious virus particles

Question 5

What are 5 general characteristics of viruses

Answer 5

• Obligatory intracellular parasites ( require living host cells to multiply)
• contain DNA or RNA
• contain a protein coat
• no ribosomes so no protein synthesis
• no ATP generating mechanism so no metabolism

Question 6

What 2 factors determine the spectrum of a host xells a virus can infect

Answer 6

Determined by specific host attachment sites and cellular factors

Question 7

Can ppl be immuned to viruses

Answer 7

yes, if they don’t have receptors for the virus on therei cells

Question 8

What are the classifications based on host

Answer 8

Bacterial viruses
Animal viruses
Plant viruses

Question 9

What are 5 viral structures

Answer 9

1) nucleic acid
2) capsid
3) nucleocapsid
4) envelope
5) spikes

Question 10

Describe viral nucleic acid

Answer 10

1) DNA OR RNA
2) single stranded or double stranded
3) linear or circular

Question 11

What is the capsid made of

Answer 11

protein coat made of capsomeres ( subunits)

Question 12

Define nuceocapsid

Answer 12

complex of nucleic acid and capsid

Question 13

What is the envelope made of

Answer 13

lipid, protein, and carbohydrates coating on some viruses

classified as enveloped virus or non envelope virus

Question 14

Define spikes

Answer 14

projections from outer surface

has surface proteins

Question 15

What in the general morphology of viruses based on

Answer 15

on the bases of their capsid shapes

Question 16

What are the 4 types of viruses

Answer 16

1) helical virus
2) polyhedral virus
3) enveloped viruses
4) complex viruses

Question 17

What are helical viruses

Answer 17

1) shaped like long rods
2) the capsids are hollow cylinders that has helical structure
3) nucleic acid coiled
ex. rabies and ebola virus

Question 18

What are polyhedral virus

Answer 18

viruses with capsids that are many sided
ex. poliovirus,adenovirus
‘plants,bacteria,anmal viruses has this shape

Question 19

Define enveloped viruses

Answer 19

enveloped and spiked and capsomes
ex. influenza ( helical)
polyhedral ( herpes virus)

Question 20

Define complex viruses

Answer 20

complicated structures
ex. bacteriophage
capsid head, sheath

Question 21

Can we grow viruses in the lab

Answer 21

yes
viruses must be grown in living cells
bacteriophages form plaques on a lawn of bacteria
plaque forming unit ( PFU)

Question 22

What are 3 ways of growing animal viruses in the lab

Answer 22

1) in living animals
2) in embryonate eggs
3) in cell cultures

Question 23

Describe embryonated egg virus growth

Answer 23

virus injected into the egg
viral growth is signaled by changes or death of the embryo
ex. flu virus, vaccines

Question 24

How are animal viruses grown in cell cultures

Answer 24

tissues treated with enzyme specific cells
infected cells detected detorioration-(cytopathic effect ( CPE))
continues cell lines are used
transformed cell grow in multiple layers

Question 25

3 techniques for viral identification

Answer 25

1) cytopathetic effects 2) seroogical tests ( western blotting) 3) nucleic acids ( RFLPs or PCR)

Question 26

2 requirements for viral multiplication

Answer 26

1) it must invade a host cell | 2) it must take over the host's metabolic machinary

Question 27

What are the 3 periods in viral growth

Answer 27

Eclipse period burst decline

Question 28

What happens in eclipse period

Answer 28

when it goes into host cell so unable to detect

Question 29

What happens during burst phase

Answer 29

when comes out of host cell

Question 30

What happens during decline in viral growth

Answer 30

when there is no more viable host cells will see a decline

Question 31

What are 2 cycles of viral multiplication for bacteriophages

Answer 31

1) Lytic cycle | 2) Lysogenic cycle

Question 32

Define lytic cycle

Answer 32

phage causes lysis and death of the host cell

Question 33

Define lysogenic cycle

Answer 33

phage DNA is incorporated in the host DNA | no cell death

Question 34

What are 5 steps of multiplication of T-even bacteriophages (Lytic cycle)

Answer 34

1) Attachement: phage attaches to host cell 2) Penetration: phages penetrates host cell and injects its DNA 3) Biosynthesis: phage DNA directs synthesis of viral components by the host cell 4) maturation: viral components reassembled into virions 5) Release: Host cell lyses and new virions are released

Question 35

What are 7 steps of multiplication of animal viruses

Answer 35

1) attachment 2) entry and uncoating.virions enter cell and its DNA is uncoated ( fusion or receptor-mediated endocytosis) 3) A portion of viral DNA is transcribed producing mRNA that encodes "early" viral proteins 4) biosynthesis. viral DNA is replicated and some viral proteins are made 5) late translation; capsid proteins are synthesized 6) Maturation virions mature 7) release virions are released via budding

Question 36

What are 2 forms of attachment and penetration

Answer 36

1) endocytosis | 2) fusion

Question 37

Define endocytosis

Answer 37

entry of toga virus by pinocytosis

Question 38

Define fusion

Answer 38

entry of herpes virus by fusion | capsid releases its DNA or RNA to work in cell

Question 39

Describe of budding of an enveloped virus

Answer 39

host cell plasma membrane create envelope

Question 40

What are 5 possible effects that animal viruses may have on cells

Answer 40

1) Transformation into tumor cell ( oncogene activation) TRANSFORMATION 2) Death of cell and release of virus LYSIS 3) Slow release of virus w/o cell death ( Persistent infection) 4) virus present but not replicating ( Latent infection) 5) cell fusion

Question 41

Describe oncogenic DNA virus (2)

Answer 41

human papilloma virus ( HPV)- cervical cancer | Hepatitis B virus(HBV)- liver cancer

Question 42

Describe oncogenic rna viruses

Answer 42

human t-cell leukemia virus (HTLV-1 and HTLV-2) -LEUKEMIA AND LYMPHOMA

Question 43

Describe viroids

Answer 43

``` short pieces of naked RNA small,circular single stranded plant disease ( potatoe spindle fiber disease) ```

Question 44

Define prions

Answer 44

proteinaceous infectious particles

Question 45

How are prions inherited and transmissible

Answer 45

ingestion,transplant, and surgical instruments

Question 46

What are 4 examples of prions

Answer 46

1) Mad-cow disease 2) Creutzfeldt-Jakob Disease (CJD) 3) fATAL familial insomia 4) sheep scrapie

Question 47

Define PrPc

Answer 47

normal cellular prion protein, on the cell surface

Question 48

Define PrPsc

Answer 48

scrapie protein' accumulates in brain cell, forming plague

Question 49

8 steps how a protein can be infectious

Answer 49

1) PrPc produced by cells is secreated to the cell surface 2) PrPsc may be acquired or produced by an altered PrPc gene 3) PrPsc reacts with PrPc on the cell structure 4) Pr Psc converts the PrPc to PrPsc 5) The new PrPsc converts more PrPc 6) the new PrPsc is taken in by endocytosis 7) PrPsc accumulates in endosomes 8) PrPsc cont. to accumulate as the endosome contents are transferred to lysosomes. The result is cell death