What virus is characterized by having RNA as its nucleic acid and employs reverse transcriptase for replication?

The virus that is characterized by having RNA as its nucleic acid and employing reverse transcriptase for replication is indeed the retrovirus. Retroviruses have a unique replication cycle that involves converting their single-stranded RNA genome into DNA using the enzyme reverse transcriptase. This DNA is then integrated into the host cell's genome, allowing the viral genes to be expressed and new viral particles to be produced.

This process is a key distinguishing feature of retroviruses, setting them apart from other types of viruses. For example, DNA viruses replicate their genomes directly and do not utilize reverse transcriptase. Bacteriophages are specialized viruses that infect bacteria and typically have DNA in their composition, while parvoviruses, which belong to a different virus family, also contain DNA rather than RNA and do not use reverse transcriptase. The ability to transpose RNA into DNA is fundamental to the life cycle of retroviruses, making them a unique group of viruses in the study of virology.