viruses
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Viruses. Homework. Cell Analogy Project due Monday 10/5. Objectives. Know the two major differences between a virus and a cell Know how a virus replicates itself. Viruses. How many viruses can the class name off the tops of our heads?. Viruses. - PowerPoint PPT PresentationTRANSCRIPT
ObjectivesObjectives
Know the two major differences between a virus and a cell
Know how a virus replicates itself
VirusesViruses
How many viruses can the class name off the tops of our heads? HIV, influenza, H1N1, rhinovirus, herpes,
HPV, smallpox, polio, chickenpox, ebola, hanta, avian influenza, SARS, hepatitis, norovirus, dengue, Epstein-Barr, marburg, filoviruses
Major viruses you probably haven’t heard of include viruses infecting other animals (SIV, foot and mouth), many plant viruses (tobacco mosaic virus), bacteria viruses like T4 phage
VirusesViruses
Is a virus another kind of bacteria?
How do they cause damage to the infected organism?
DefinitionDefinition
Virus = a microscopic infectious agent that replicates but is not truly alive**By most scientists’ reckoning
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VirusesViruses
Viruses are not cells. They have only two real parts, and
only one of them can also be found in cells.
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VirusesViruses
They consist of a protein capsid (envelope or shell) that contains genetic material. Often this genetic material is DNA,
like a cell. Sometimes it’s closely-related RNA instead, in what are called retroviruses.
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VirusesViruses
This means cells have what parts that viruses don’t?
What does this mean that viruses cannot do for themselves?
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VirusesViruses
A virus can do one thing and one thing only: they force a cell (a host) to make more copies of the virus.
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Viral ReplicationViral Replication
http://videos.howstuffworks.com/hsw/8061-viruses-how-viruses-work-video.htm
http://www.hhmi.org/biointeractive/media/viral_lifecycle-lg.mov
http://student.ccbcmd.edu/courses/bio141/lecguide/unit3/viruses/adlyt.html
In spite of this, it’s not usually lysing cells that cause pain and symptoms, but it’s actually the body’s defense mechanisms that cause discomfort.
CheckpointCheckpoint
How is a virus different from a cell?
How is viral replication different from how a cell can reproduce?
Viruses in HistoryViruses in History
Smallpox and the destruction of Native American civilizations Mexico’s population: 18 million to 1.6
million in 100 years American & Canadian Nations
reduced to 5% of former population (20 million) in 200 years
Smallpox eradication in 20th century
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Viruses in HistoryViruses in History
Influenza Pandemic of 1918 http://videos.howstuffworks.
com/hsw/8063-viruses-the-influenza-pandemic-of-1918-video.htm
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Viruses in HistoryViruses in History HIV pandemic
HIV mutated from SIV The more closely related two species are, the
easier it is for them to share viral illnesses Discovered in the 1980s, 25 million dead
since 1981 1/3 in Subsaharan Africa, ~6% children
Fast mutating, no cure or vaccine yet. Clearly understood transmission & pathology Many treatments & application of evolutionary
principles mean it’s no longer “a death sentence” with medical assistance, but still a pandemic.
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Viruses in HistoryViruses in History
Applications in Biotechnology Knowing what you do about how a
virus replicates, why do you think scientists look to viruses to help treat genetic disorders?
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Unanswered QuestionsUnanswered Questions
Last remaining stores of smallpox in U.S. and Russia?
Herd immunity vs. individual freedoms - parents refuse vaccination for children?
Viruses used to modify genes for agriculture, medicine?