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Viruses: Biology at the NanoScale
VIRUSES: What are They?
viruses (n.) Any of various simple submicroscopic parasites of plants, animals, and bacteria that often cause disease and that consist essentially of a core of RNA or DNA surrounded by a protein coat. Unable to replicate without a host cell, viruses are typically not considered living organisms. |
American Heritage Dictionary of the English Language – Fourth Edition |
NEW! Virus Animation
Learn about viruses through our new animated powerpoint presentation. Watch a phage invade a bacterium. Learn about how viruses take over a cell and multiply. Examine different virus structures and learn about the history of virology research.
http://www.cs.unc.edu/Research/nano/ed/powerpoint12-8-2003.zipAre Viruses Living or Non-living?
This is a difficult question to answer because we have yet to define what it means to be living. Does having a DNA mean that it is living? Does having the ability to reproduce mean that it is living? Does needing food and metabolising mean that it is living?
Clearly, viruses are more complicated than chemical molecules. Yet, much simplier than the most basic single cell organism. Similar to organisms, viruses are made up of proteins and nucleic acid which are organic compounds. Some viruses have a lipid membrane. They evolve and mutate. A virus has the potential to reproduce with the aid of their host cell, but does not need energy to persist, i.e. does not need food.
So for now, depending on how YOU define living, a virus can be either living or non-living.
Virus Structure
Viruses are nucleic acid coated with proteins. The nucleic acid can be either RNA or ss-DNA or ds-DNA. The protein coat is typically an assembly of one to several protein subunits.
*Priniciples of Virus Architecture [http://web.uct.ac.za/depts/mmi/stannard/virarch.html]
What do Viruses Infect and How?
Viruses can infect many living organisms from bacteria to plants to animals. However, a single type of virus can not infect all cell types. When a virus infects a cell, the virus forces the cell to make many copies of that virus. It does this by inserting the viral genome into the cell.
Why are viruses dangerous and not?
Of course, wild-type viruses are dangerous because they can make you very sick and even cause death. Surprisingly, these same viruses can be used to help cure diseases rather than causing them. Scientists have found ways to modify the virus so that it acts as a gene vector rather than a parasite. They remove the viral genome so that the virus can no longer replicate and replace it with human genome that is defective in the diseased cell.
*Virus Vectors & Gene Therapy
[http://www.tulane.edu/%7Edmsander/WWW/335/peel/peel1.html]NOT A VIRUS!
Because they both infect and cause diseases, viruses are sometimes confused as bacteria and vise versa. However, they are very different. We can treat bacterial infections with antibiotics, but not viral infections. Bacteria are much bigger and can be infected by viruses.
*Oh Goodness, My E.Coli has a Virus!
[http://www.cellsalive.com/phage.htm]Cool Virus Links
*Viology on the WWW
[http://www.tulane.edu/%7Edmsander/garryfavweb.html]
*The Big Picture Book of Viruses
[http://www.virology.net/Big_Virology/BVHomePage.html]
*Animations of HSV Infection and Replication
[http://darwin.bio.uci.edu/%7Efaculty/wagner/movieindex.html]
