BIOL 191 Introductory Microbiology
Chap. 13 Viruses, Viroids and Prions Study Guide
I.
General Characteristics of Viruses
a. Intro
i. Table 13.1 Comparing Viruses and Bacteria
Are viruses… Are typical bacteria…
Intracellular parasites?
Do they have a plasma membrane?
Do they contain ribosomes?
Do they reproduce by binary fission?
Do they possess both RNA and DNA in the same
structure?
Are they sensitive to antibiotics?
Are they sensitive to interferons?
ii. *Obligatory*intracellular*parasites*: What does this
mean?
iii. Define virus
b. Host Range. What does the host *range* depend on? What is
a bacteriophage?
c. Viral Sizes Fig. 13.1 What is the typical viral size?
II.
Viral Structure -
Define ‘Virion’
Will a virus survive outside of the cell and be able to transmit to
another host if it is not in this form?
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a. Nucleic Acid –
i. Genetics
Chap. 8 pp. 211-212, Fig. 8.2 p. 213 The Flow of Genetic
Information Know the basics of DNA expression and
replication. These processes are necessary for viral
multiplication.
ii. What types of nucleic acids may viruses have? See Table
13.2
b. Capsid
c. Envelope
d. Spikes
-Influenza examples:
1. H (Hemagglutinin) proteins
Hemagglutinin is one of two virally-coded integral envelope proteins of the influenza
virus. Hemagglutinin is responsible for host cell binding and subsequent fusion of viral
and host membranes after the virus has been taken up. In the first step of infection it
binds to receptor proteins on target cell surfaces and later promotes the release of the flu
virus into the host cytoplasm.
http://www.callutheran.edu/BioDev/omm/jmol/ha/ha.html#intro
2. N (Neuraminidase) proteins2
Projections from surfaces of influenza viruses containing neuraminidase are involved in
the release of viruses from infected cells.
Mosby's Medical Dictionary, 8th edition. © 2009, Elsevier.
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Be able to recognize and label these morphological forms of viruses.
Polyhedral
Helical
Complex
Enveloped
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III.
Taxonomy of Viruses
a. What is ‘taxonomy’?
b. How does the International Committee on Taxonomy of
Viruses group viruses?
c. What is a viral species?
IV. Isolation, Cultivation and Identification of Viruses
a. How are bacterial and animal viruses grown in the lab?
b. What are some ways viruses are identified?
V. Viral Multiplication: First bacteriophage, then animal viruses
Chap. 8 Microbial Genetics: Using your textbook, in Chap. 8, be sure you know what
DNA replication, Protein synthesis (transcription/translation), mRNA, tRNA, and rRNA
refer to
What genes do viruses have? What enzymes do virions contain?
A. Multiplication of Bacteriophages
a. T-Even Bacteriophage Lytic Cycle
i. Know general info about the T-even bacteriophages
ii. Fig. 13.11 The lytic cycle of a T-even bacteriphage
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Know the steps of the lytic life cycle:
Attachment
Penetration
Biosynthesis
Maturation
Release
iii.
iv.
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b. Bacteriphage Lambda Lysogenic Cycle (temperate phages)
Know the steps and alternatives of the lysogenic cycle:
Fig. 13. 12 The lysogenic cycle of bacteriophage lambda in E. coli
Attachment
Phage DNA circularization
Lytic
Lysogenic
Prophage formation
What happens when the bacterium reproduces?
Can lysogenic viruses be lytic?
What are important possible results of lysogeny?
Chap. 8 Fig. 8.28 Generalized transduction, in which any bacterial
DNA can be transferred from one cell to another.
Fig. 13.13 Specialized transduction, in which only DNA on either
side of the prophage DNA can be transferred.
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B. Multiplication of Animal Viruses
a. How do animal viruses differ from phages? Table 13.3and
text discussion
b. Why might some people be resistant to a specific virus but
not others? How is ‘attachment’ related to drug
development against viruses?
c. Know the steps and alternatives of animal virus
multiplication
i. Attachment
ii. Entry
iii. Uncoating
iv. Biosynthesis
1. Biosynthesis of DNA Viruses
a. Fig. 13.15 Foundation Fig. Replication of
a DNA-Containing Animal Virus
b. Know text discussion of the Families
Herpesviridae and Papovaviridae
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2. Biosynthesis of RNA Viruses
a. Fig. 13.17 Pathways of multiplication
used by various RNA-containing viruses
b. Know text discussion of Retroviridae
Fig. 13.19 p. 390
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v. Maturation and Release
1. Cell Rupture
2. Budding
C. Compare Bacteriophage and Animal Virus Multiplication
Table 13.3
D. Comparison of DNA & RNA Viruses
Table 13. 4
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VI. Viruses and Cancer
A. Define oncogenes, oncogenic viruses (oncoviruses),
Transformation, Transformed cells
B. What % of cancers is known to be virus-induced?
C. DNA and RNA Oncogenic Viruses: Know examples from the text
discussion
VII. Latent Viral Infections: Define and know examples from text discussion
Fig. 13.21 Latent and persistent viral infections
VIII. Prions
See Fig. 13.22 How a protein can be infectious
A. Know examples and how they are different from viruses
B. Nervous System Diseases caused by Prions Chap. 22 p. 629-632
IX. Plant Viruses and Viroids
A. Know general info
B. Why are plants somewhat protected against many diseases?
C. Define viroid
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