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Are viruses alive or
dead?
- –Are complex chemicals outside cells
- -Are living entities within live cells
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Properties of viruses?
Obligated intracellular paracites; not composed of cells. Made of single nucleic acid (DNA or RNA) surround by protein coat. Multiply using cell synthetic machinery
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Size of viruses?
- Diameter: 20-1000 nm
- lenght- up to 14,000 nm
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Bacteriophages are what?
A bacterial virus; also called phages.
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What is the viral protein coat called?
Capsid
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Protein subunits of the capsid are?
Capsomere
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What is a virion?
complete, fully developed, infectious viral particle.
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Viral nucleic acid (the genome) can be?
- DNA or RNA (never both)
- Non-segmented or segmented
- Linear/cicular
- Double stranded/singled stranded
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Helical Viruses?
- - Long or curved rods/threads
- e.g. TMV, rabies virus, etc
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Polyhedral viruses?
Icosahedron structure (many sided)
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Enveloped Viruses?
Surrounds the capsid and derived from cellular membranes.
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Complex viruses?
- have complex structures.
- ex. T-even phages, and poxviruses
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Animal Viruses can be grown?
Lab animals, embryonated eggs and cell cultures
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Cytopathic effect (CPE) is?
A visable effect on a host cell, caused by a virus that may result in host cell damage or death.
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Primary Cell Line?
Cells with finite lifespan, cultured directly upon removal from animal
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Continuous Cell Line?
Immoratalized cells; grow indefinitely in culture.
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What are the steps in Viral Multiplication?
- 1) Attachment
- 2) Penetration
- 3) Uncoating
- 4) Biosynthesis
- 5) Maturation
- 6) Release
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Bacteriophage multiplication?
- Lytic and Lysogenic cylces are present depending on virus type.
- - only lytic cylce in T even phages
- - Both cycles in lambda phages
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Lytic cycle?
Ends with lysis and death of host cell
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Lysogenic Cycle?
Phage DNA becomes inserted in host cell genome as prophage
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Transduction?
The transfer of DNA from one cell to another by a bacteriphage.
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Animal Virus Multiplication?
- DNA Viruses- multiply the nuclues; host enzyme transcribes viral DNA to give mRNA
- RNA Viruses- multiply in cytoplams
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Why is viral cause of cancer difficult ot diagnose?
Viruses are difficult to see and many infect cell withoust causing caner. Cancer are not contagious and may not develop until long after viral infection is established
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Oncogenic viruses?
Viruses that cause cancers
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What happens to cells when they are affected with cancer?
Loss of contact inhibiton, chromosome changes, tumor specific transplantation antigens, and T- antigens
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Latent viruses?
Reamins for long period of time w/o disease. Infectious virus appear suddenly but usually not fatal.
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Slow/Persistent viruses?
occurs over long period of time. Infectious virus gradually builds up. Usually fatal.
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Prions?
are caused by infectious proteins called prions. Noraml cellular proin proteins is changed bye an abnormal scrapie protein.
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Viroids?
Plant disease cause by naked RNA
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