Final answer:
Retroviruses, such as HIV, require the reverse transcriptase enzyme to convert their RNA genome into DNA, which is then inserted into the host cell genome.
Step-by-step explanation:
The viral class that requires the reverse transcriptase enzyme is retroviruses, such as HIV. Retroviruses, such as HIV, require the reverse transcriptase enzyme to convert their RNA genome into DNA, which is then inserted into the host cell genome. Retroviruses have an RNA genome that needs to be reverse transcribed into DNA, which is then incorporated into the host cell genome.
The enzyme reverse transcriptase is encoded by viral genes and transcribes an RNA template to DNA. Reverse transcription never occurs in uninfected host cells, as the enzyme is only derived from the expression of viral genes within the infected host cells.