Virus Group

April Boykin, Brooks Cleaton, Rob Knapp, and Lorenzo Baxter

Introduction to viruses:

    In ancient Rome, virus meant "poison" or "venomous secretion."  Viruses are unlike anything else that, we as humans, can find on Earth.  Viruses are characterized by shape, size, and their half dead/half alive existence.  They are so small that they can only be viewed through a microscope.

Characteristics of Taxon

Facts about viruses:

•     Viruses can infect everything from humans to bacteria
•     It is a non-cellular infectious agent that has a protein coat surrounding a nucleic acid core with genetic material inside
•     The virus cannot reproduce itself on its own so it must have a host cell
•     Viruses contain protein that bind with specific receptors on host
•     Viruses are so small that the largest virus is equal in size to the smallest bacteria known to man

This is the design of a protein shell.

Bacteriophages

•     Most knowledge about viruses comes from bacteriophages
•     They are cultured living host cells for studying viruses

Multiplication of Viruses

    The multiplication of viruses is interesting considering that viruses are not even alive.  Viruses need host cell to reproduce.  There are five basic steps in the multiplication process of viruses.  They are as follows:

1. Attachment- The virus attaches itself to a host cell.
2. Penetration- The whole or partial virus enters the cells cytoplasm.
3. Replication and Syntheses- DNA or RNA directs host cell into producing many copies of viral nucleic acids and proteins.
4. Assembly- Viral nucleic acids and viral proteins are put together to form new infectious particles.
5. Release- New virus particles are released from the particles.

Pathways of Multiplication

Lytic- The plasma membrane and cell wall of the host is damaged so that the cytoplasm leaks out and the cell dies

Lysogenic- The viral enzyme cuts the host chromosome and then injects its viral genes into the host cell.  Then when the host cell begins to divide, the recombinant DNA is replicated. Lateron, the environment could turn on the daughter cells and then they reactivate the cycle.

RNA Viruses

In the host cell the virus can assemble DNA on viral RNA.  Thus, reversing the transcription of the host cells DNA making it work against itself.  An example of this is the retrovirus HIV.

Interesting Species

The picture on the left illustrates one of the most common viruses, the flu virus.  To the right we have a virus that causes the tobacco mosaic disease.  

Type 1 herpes simplex is an example of a lysogenic multiplication.

Above, there is the ebola virus (right) and the Rotavirus (left).

Roles in the Environment

Viruses can infect anything living.  This means that everything on the planet that is alive is at risk of being infected with viruses.  This is not always a bad thing.  Because viruses can kill cells by lytic multiplication, organisms need a defense.  Their only defense is to adapt.  This creates diversity among species thus making communities more hardy.

Works Cited

Murray, A. G.2001. http://seaweed.ucg.ie

Weslake High School, MD. 2001. www.library.thinkquest.org-google-search

Grefsheim, Suzanne 2001. http://nihlibrary.nih.gov/resourceindex.htm

Haunch, Niki 2001. http://www.leeds.ac.uk/lmi/ebv/links.html

Q. P. Design 2001. http://hivdent.org

Robert M. Bock Laboratories 2001. http://www.bocklabs.wisc.edu/

University Of  South Carolina School Of Medicine 2001. http://www.med.sc.edu/