n triggering cancer. Proto-oncogenes induce cell growth and reproduction, while tumor suppressor genes inhibit it. Together, they carefully control the proliferation of cells. However, if a proto-oncogene is mutated, it can become a carcinogenic oncogene, driving excessive multiplication. Tumor suppressor genes, on the other hand, contribute to cancer when they are inactivated by mutation (Ruddon, 1995). Luckily, cancerous tumors are not caused by one little mutation in one cell – they are caused by multiple mutations in a number of the cell’s growth-controlling genes. The number of mutations necessary can be as low as two or quite high, depending on the specific type of cancer. Generally, these mutations occur either from mistakes during cell reproduction, or due to DNA damage caused by carcinogens such as tobacco, certain poisons, and UV rays. So, why don’t we all get cancer from these things right away? Consider that one of your cells is damaged by poison and becomes mutated. In order for this cell to turn into a cancer cell, the rest of the necessary mutations must also occur in this very same cell. This in itself, is fairly unlikely. It normally takes decades for an incipient tumor to collect all the mutations required for it’s malignant growth, which explains why the average age for cancer diagnosis is 67 (Ruddon, 1995). Why, then, do some individuals contract cancer before the typical age of onset? In many cases, this is explained by the inheritance of a mutation in a critical growth controlling gene. Typically, this mutation would be a very rare event. However, in this individual, the mutation is present in ALL the cells of the body, instead of in some randomly stricken cell. So, the process of tumor formation skips it’s first, slow step. No one can actually inherit cancer; rather, they inherit a predisposition to develop a cancer, which is why cancers do tend to run in families, ...
