And a special thing about this RNA molecule is it contains the genetic information that codes for a special protein known as RNA directed RNA polymerase. Now, remember, inside our bodies we take the DNA and we form the RNA molecule by using a special type of RNA polymerase. But inside these viruses this RNA polymerase actually transcribes RNA molecules from other RNA molecules and not DNA to RNA as it takes place inside our cells of the body. So there are many examples of viruses in nature that follow this same pathway that is followed by the tobacco mosaic virus. That is, they form RNA agents or RNA molecules from other RNA molecules. Now, another interesting category of viruses are the retroviruses and one example of a retrovirus is HIV.