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[[Image:Virus.jpg|right|350px|thumb|Microscopic view of a virus.]]

[[Image:Virus.jpg|right|350px|thumb|Microscopic view of a virus.]]

A '''virus''' is a tiny non-[[cell]]ular infectious agent that has two characteristics: It has genetic material (either [[DNA]] or [[RNA]]) inside a protective [[protein]] coat.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref> To reproduce itself, it needs to infect a cell. The genetic material is inserted into the cell, and the reproductive machinery of that cell is then effectively "hijacked": the cell starts to produce components of new virus particles. These components spontaneously self-assemble and the new virus particles can then infect other cells, where the same process happens.  This infection cycle has two forms.  One a virus will implant its DNA in the host cell's and wait until the cell is under stress and then begin to copy more of itself.  This method allows for the virus gene (called the pro-phage) to continue through multiple generations of cells until the correct replicating time has arrived.  The other method involves a virus directly injecting its genetic material into the cell and immediately forcing it to make viral copies.  After about 200 virues have been produced the cell lyses (explodes) and the copies are now free to infect more cells.

A '''virus''' is a tiny non-[[cell]]ular infectious agent that has two characteristics: It has genetic material (either [[DNA]] or [[RNA]]) inside a protective [[protein]] coat.<ref>Wile, Dr. Jay L. ''Exploring Creation With Biology''. Apologia Educational Ministries, Inc. 1998</ref> To reproduce itself, it needs to infect a cell. The genetic material is inserted into the cell, and the reproductive machinery of that cell is then effectively "hijacked": the cell starts to produce components of new virus particles. These components spontaneously self-assemble and the new virus particles can then infect other cells, where the same process happens.  This infection cycle has two forms, lysogenic and lytic.  In the lysogenic a virus will implant its DNA in the host cell's and wait until the cell is under stress and then begin to copy more of itself.  This method allows for the virus gene (called the pro-phage) to continue through multiple generations of cells until the correct replicating time has arrived.  Viruses that use this cycle are said to be 'latent' and are often retroviruses (their genetic material is RNA, as opposed to DNA).  An example of this type of virus would be the HIV virus.  The other method (the lytic cycle) involves a virus directly injecting its genetic material into the cell and immediately forcing it to make viral copies.  After about 200 virues have been produced the cell lyses (explodes) and the copies are now free to infect more cells.  Many of these viruses are bacteriophages.  This is because bacterium have a cell wall that does not allow the absorbtion of the virus like the [[plasma membrane]] of animal cells do, forcing the virus to inject only its genetic material.

Even though viruses can reproduce, they are not considered alive since they do not feed, respire, grow, or move.

Even though viruses can reproduce, they are not considered alive since they do not feed, respire, grow, reproduce (by themselves) or move under their own power.

Examples of viruses include the [[influenza]] virus, the common cold, [[smallpox]] and [[polio]].

Examples of viruses include the [[influenza]] virus, the common cold, [[smallpox]] and [[polio]].