Cancer is the uncontrollable, destructive reproduction of cells in an organism. When a cell becomes cancerous it begins to divide rapidly. Soon there are so many of these cells that they begin to damage the surrounding tissue. This harmful mass, called a tumor, can often prove fatal.

Cancer has always been a threat, but only recently have we begun to understand what causes it. In our bodies we have many genes that control our growth and cell reproduction rate. These genes are activated whenever it is necessary for a cell to divide. Some of these genes, though, if mutated slightly, can become permanently switched into the "on" position causing the cell to reproduce constantly and become cancerous. Scientists have discovered more than fifty of these structures known as oncogenes. The root of cancer, then, is lying dormant within us. Some oncogenes require only one single point mutation to become dangerous. This mutation could be triggered by a number of factors - x-rays, sunlight, tobacco, chemicals, viruses, etc.

There is an alternate, equally dangerous form of cancer that is largely the reverse of the oncogene threat. Our bodies (and the bodies of other organisms) contain genes that tell our cells when to stop growing. These genes, known as tumor suppressor genes, sometimes become stuck in the "off" position, causing the cell to grow and reproduce uncontrollably. Again, this cell growth forms a tumor and can prove fatal.

Luckily, cells don't generally become cancerous unless a combination of genes is affected as described above. This is why cancer often strikes individuals late in life after they have had more time to be exposed to a variety of carcinogens. Unfortunately, the fact that there are so many health threats in our world today makes cancer somewhat harder to fight - there is no one danger that we must beware of. This disease can be caused by a great number of things, and its seed is buried deep within our own genetic makeup.