Card Set Information
Define virion, prion, and viroid, and phage
: complete, infectious virus
: Infectious protein
: Infection RNA (plant pathogen)
: virus that infects bacteria
Describe morphological classes of viruses and give an example of each
: long rods with hollow cylindrical capside (Ebolavirus, rabiesvirus)
: many-sided capsids (adenovirus, poliovirus)
: has additional structure attached to capsid (bacteriophage T4)
Define plaque forming unit, Explain the plaque method (its uses and procedures)
Viruses must be grown in living cells
: clearing in plate caused by lysing of bacteria as viruses multiply
: theory that each plaque initially came from a single virus
: PFUs counted and viruses determined in that manner
Define lysogenic conversion and give examples of diseases that result from this
Lysogenic (phage) conversion
: host cell exhibits new properties (production of toxins by prophage)
Scarlet fever, diptheria, and botulism can result
List and describe the 5 steps of viral multiplication (lytic cycle)
: phage attaches to host cell
: phage penetrates host cell and injects DNA
: Phage DNA directs synthesis of viral components by the host cell
: viral components are assembled into virions
: host cell lyses, and new virions are released
Compare and contrast lytic and lysogenic cycles
: phage DNA not incorporated into host DNA, causes lysis and death of host cell
: phage DNA incorporated in host DNA (prophage), host is not killed, phage conversion can occur, specialized transduction can occur upon excisement.
Differentiate between specialized and generalized transduction
: Prophage is within the chromosome. Excises innapropriately from the chromosome and takes a gene with it.
: Bacterial chromosome broken to pieces during viral construction, accidentally packaged into virus and released.
Explain the mechanism by which some viruses (retroviruses) induce tumors (cancer) give examples
Lysogenic cyle integrates DNA into host's DNA, which can alter the nucleotide sequence forming infections and cancers.
The cell recieves new properties which lead to increased growth and loss of contact inhibition.
: adenoviridae, herpesviridae, poxviridae, palpvaviridae, hepadnaviridae
: retroviridae, HTLV-1, HTLV-2
Explain the importance of reverse transcriptase and describe what occurs in the biosynthesis of a virus with reverse transcriptase
Reverse transcriptase is necessary for retroviridae to infect the host cell. RNA is converted to DNA, and the DNA is inserted into the host cell's chromosome.
The reverse transcriptase enzyme is packaged within the viral capsid during biosynthesis.
Describe how the following are cultured in the laboratory: bacterial viruses (bacteriophages), animal viruses
: plaque method (clearing zone is 1 PFU)
: living animals, embryonated eggs, or cell culture (plants or animals)
List the major methods used for viral identification
: destruction of cells
: detect antibodies against viruses in a patient (neutralization tests, viral hemagglutination, Western blot)
: RFLPs (similar to DNA fingerprinting), or PCR (specific viral sequences)