Viruses are a scientific puzzle. Scientists are still trying to figure out if they are alive are not. Viruses seem to be alive because they have a nucleus and D.N.A. or R.N.A. (ribonucleic acid) wrapped in a few protective layers. They don't seem to be alive because they don't grow, feed, move, or eat except when they are in the cell. All a virus is programed to do is to make more viruses. It works kind of like an alien ship attacking a planet.
Here is an animation of a virus attacking an animal cell. In
this animation, the spaceship represents the virus and the planet
represents the healthy cell. Here is how
it works in an animal cell:
1.The virus gets into your body. The
flu virus, for example, gets into your body traveling through
the air in tiny droplets of water, and you breathe it in.
2. Once the virus is in your body, the virus attacks a healthy
cell and injects its D.N.A. or R.N.A. into it.
3. The new viruses start to grow inside the cell.
4. The new viruses grow until they've used up all the cell's nutrients.
5. The cell bursts and all of the new viruses go out to make more
viruses in new cells.
The viruses can cause AIDS, chicken pox, colds, cold sores, hepatitis (a liver disease), measles, mumps, rabies, and yellow fever. Viruses aren't all bad though. Actually, they are finding useful ways to use them. Believe it or not, they have used a virus to cure Cystic Fibrosis in one person in 1993. Cystic Fibrosis is a disorder that effects the cells and glands that produce tears, mucous, sweat, digestive juices, and saliva. Lung diseases and lung damage are the worst consequences of Cystic Fibrosis. Doctors were able to find the gene that causes Cystic Fibrosis. Scientists then took the correct D.N.A. from a healthy person and injected it into a virus. The person then inhaled the virus which injected the correct gene into the victim's cells. The person became well. Scientists are still deciding whether to treat other people this way and whether or not to use viruses as a carrier for the correct genes.
Did you know that plants can get viruses too? In fact, viruses can cause very serious damage to crops. The diseases the plant might get include tobacco mosaic and turnip yellows mosaic. Here is how it works:
1. The virus can't get through the cell
wall of a plant cell, but insects can. Insects penetrate the cell
wall when feeding on the plant. The viruses can then get into
the plant and through the cell membrane.
2. The virus injects its D.N.A./ R.N.A. into the cell.
3. The new viruses start growing inside the cell.
4. The new viruses grow until they have used up all the cell's
nutrients.
5. The cell bursts and all of the new viruses go out to make more
viruses in new cells.