Which of the following describes a retrovirus?

A retrovirus is uniquely characterized by its use of reverse transcription during its replication cycle. This means that a retrovirus carries its genetic material in the form of RNA. Upon entering a host cell, it utilizes an enzyme called reverse transcriptase to convert its RNA into DNA. This newly synthesized viral DNA is then integrated into the host's genome, allowing it to hijack the host's cellular machinery for the production of new viral particles.

This characteristic distinguishes retroviruses from other types of viruses; for instance, viruses that contain DNA do not undergo this reverse transcription process. Additionally, while some viruses may infect bacteria, retroviruses specifically target eukaryotic cells, particularly those in higher organisms. Finally, all retroviruses possess a protein coat (capsid) that protects their RNA and facilitates the entry into host cells, contrary to the choice suggesting a retrovirus lacks a protein coat. Thus, the correct answer highlights the defining feature of retroviruses and their unique replication mechanism.