Viruses are thought to play a role in roughly 15 percent of all cancers. The first such connection was made in the early 1900s with the discovery of viruses associated with cancer in chickens.

Recall that viruses are made of genetic material, either DNA or RNA. They can cause disease in the host organism while they replicate their genetic material within its cells. In addition to causing infectious disease, viruses have another way of disrupting normal body functions. Viruses can interfere with normal DNA repair mechanisms, directly change the cell's gene sequence, or cause rapid cell division that encourages mutations. All of these changes can stimulate the uncontrolled cell division that is the hallmark of cancer.

It's not known why some people infected with a certain virus develop cancer while others do not. Scientists are studying this question and trying to develop vaccines against some of these cancer-associated viruses.

In this lab, you will research the characteristics of one of these viruses using the Internet.

How are some viruses and some cancers related?

• Start by using Wikipedia to begin your search
• Develop a list of two human viruses and one animal viruses implicated in cancer
• Use one of the viruses on your list to complete the attached document