A class of virus that contains RNA and not DNA as its genetic material. Retroviruses produce an analogue (a kind of mirror image) of their RNA by using an enzyme known as "reverse transcriptase." The result of this capability is DNA that incorporates itself into the genetic material of the cell that the virus has invaded. The virus believed to cause AIDS, HIV, is a retrovirus. It is hoped that by thwarting this "reverse transcriptase" scientists will be able to prevent the retrovirus from replicating itself in the host cell.