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22 Cards in this Set

  • Front
  • Back
Viruses
Acellular
Viruses contain DNA or RNA
Surrounded by a protein coat (capsid)
Some are enclosed by an envelope with spikes
Most viruses infect only specific types of cells in one host
Host range is determined by specific host attachment sites and cellular factors
Virus Size
Virus Structure
Nucleic acid (genetic information)
DNA or RNA

Capsid
Protein subunits (protomers or capsomeres)

Nucleocapsid : capsid plus nucleic acid

Envelope (peplos) with spikes (peplomeres)
Helical viruses
rod shaped
capsomers arranged in a helix
Complex viruses
both helical and polyhedral components
bacteriophages
poxviruses
Unknown symmetry
Growing Bacterial Viruses
Viruses must be grown in living cells

Bacteriophages infect bacterial cells and form plaques on a lawn of bacteria.
Bacteriophage T4
first discovered and most studied bacteriophage
Multiplication of Bacteriophages (Lytic Cycle)
Steps 1-3
Multiplication of Bacteriophages
Steps 4-5
One-step Growth Curve
Taxonomy
Viruses are grouped into families based on similar physical properties

EX:
DNA or RNA

capsid morphology

enveloped or naked

ds or ss nucleic acid

if ss RNA is it + or –

if ds DNA id it circular or linear

Family names end in -viridae
Growing Animal Viruses
Viruses must be grown in living cells

live animals
enbryonated eggs
tissue culture (eucaryotic cells)
Tissue Culture
Animal viruses may also be grown in cell culture.

Normal cells or primary cells are grown in monolayers on plastic

Transformed or continuous cell cultures form foci
Multiplication of Animal viruses
Penetration and Uncoating by fusion
Penetration and uncoating by fusion
simultaneous in time
Entire Nucleocapsid enters cell
Penetration and Uncoating by endocytosis
Penetration by endocytosis
Entire nucleocapsid enters cell
Multiplication of a DNA –Containing Animal Virus
RNA-Containing Viruses
RNA viruses must code for RNA Dependent RNA Polymerase
no RDRP present in cells
RNA —> RNA
Multiplication of a Retrovirus
Retroviruses
RNA viruses that can make DNA
RNA —> DNA
Require reverse transcriptase (RDDP)
RNA dependent DNA polymerase
Retrovirus Phase I (integration)
Phase I (integration) is under control of the virus
viral RDDP converts vRNA to vDNA
viral integrase inserts vDNA into cell chromosome
Retrovirus Phase II (multiplication)
Phase II (multiplication) is under control of the cell
cell DDRP transcribes viral message from provirus
cell ribosomes translates viral message into viral proteins
virus assembles and buds from cell