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Virus Structure and Function - Coggle Diagram
Virus Structure and Function
Characteristics & History
viruses are obligatory intracellular parasites
virus contains nucleic acid (RNA or DNA), and a protein coat
viruses do not have a plasma membrane, do not reproduce by binary fission, and can't generate ATP, are sensitive to interferon
1866 Adolf Mayer- Tobacco Mosaic Disease could be transmitted from plant to plant
1892 Dimitri Winooski- filtered sap of of tree and found fluid was diseased. Filterable Agent.
yellow fever was first "filterable agent" and first disease caused by a virus
1901 Walter Reed- Yellow Fever 1st to demonstrate transmission by mosquito. (vector)
Structure and Genetics
virion is a complete, fully developed, infectious viral particle
protein coat around NA is the capsid- composed of capsomeres
envelope round capsid. consists of part of host cell membrane with proteins coded for by the virus
nonenveloped viruses consist of nucleic acid and capsid
spiked are carbs and proteins that project from envelope.
Viral Morphology and Host Range
Polyhedral virus: often an icosahedron (20 equilateral triangles), poliovirus or adenovirus
Helical Virus: examples include filovirus (Ebola) and lyssavirus (rabies)
Enveloped Icosahedral Virus: Herpesviridae: cold sores, chicken pox, shingles
complex virus: dsDNA, enveloped, large, T-bacteriophage
most are species specific, but some have a broad host range
bacteriophages infect only bacteria. attachment sites: cell wall, fimbriae, or flagella
receptor sites: proteins, glycoproteins of plasma membrane
Viral Replication
Animal virus: entry is by pinocytosis or fusion for enveloped viruses. uncoating is done by lysosomal enzymes
POX virus replicated DNA in cytoplasm
lytic cycle ends in death of host cell
lysogenic cycle involves insertion of phage DNA into host genome, forming prophage.
lysogenic cycle: phage remains latent and host remains alive
result of lysogeny: phage conversion: host cell may exhibit new properties. producing the disease only when prophage is present. codes for cytotoxin
Yellow Fever
Yellow Fever is caused by Flavivirus. zoonotic disease
the sylvatic cycle involves mosquitoes transmitting the disease from monkeys to humans.
the urban cycle involves mosquitoes transmitting disease from human to human
prevention includes vaccine and mosquito control
Influenza
Orthomyxoviridae has a genome composed of
_
separate RNA segments
H spikes allow virus to attach to specific host cell receptors
N spikes help the virus separate from infection cells after replication
TMT treatment includes neuraminidase inhibitors
Special Viral Mechanisms
antigenic shift: major genetic recombination. mixing of RNA segments. can cause new virus
antigenic drift: minor annual variations in antigenic makeup of influenza. alteration of a single a.a. of H or N spike.
latent viral infections: activated by stress.
retrovirus- RNA virus- carry reverse transcriptase which uses RNA as template for dsDNA. DNA can be inserted into host cell as a provirus