Retrovirus
Retrovirus, any virus belonging to the family Retroviridae, whose members share a unique method of replicating themselves when they infect living cells. Retroviruses store their genetic information in molecules of ribonucleic acid (RNA). However, unlike other RNA viruses, retroviruses use RNA as a template (master pattern) for forming deoxyribonucleic acid (DNA), the genetic material that puts viral replication instructions into effect. This process, called reverse transcription, is the exact opposite of the normal flow of genetic information in living things in which DNA serves as the template for RNA formation. Retroviruses affect a wide range of animals, although the best-known types are those that target vertebrates. Some retroviruses are harmless, but many can cause malignant transformation—a genetic change that makes healthy cells cancerous. Disease-forming retroviruses can cause diseases such as leukemia in mammals and malignant tumors and other disorders in birds. From a hu...