Viruses

Viruses

HomeworkHomework

Cell Analogy Project due Monday 10/5

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?

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.



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.







VirusesViruses

This means cells have what parts that viruses don’t?

What does this mean that viruses cannot do for themselves?







VirusesViruses

A virus can do one thing and one thing only: they force a cell (a host) to make more copies of the virus.





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








Influenza Pandemic of 1918 http://videos.howstuffworks.

com/hsw/8063-viruses-the-influenza-pandemic-of-1918-video.htm



http://videos.howstuffworks.com/hsw/8063-viruses-the-influenza-pandemic-of-1918-video.htm




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.






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?



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?

Documents

Viruses