Q. Is there any situation in which the DNA is made based on the RNA template? What is the enzyme involved?
The process in which the DNA is synthesized having as template a RNA chain is known as reverse transcription. In cells infected by retroviruses (RNA viruses, like the SARS or AIDS viruses) reverse transcription occurs and the DNA is made from information contained in the viral RNA.
Viral RNA within the host cell produces DNA with the help of an enzyme known as reverse transcriptase. Based on that the DNA the host cell then makes viral proteins, new viruses are assembled and viral replication occurs.