Which of the following best describes the action of retroviruses such as HIV?

• A. They directly translate their RNA genome into proteins without any DNA intermediate.
• B. They infect only bacterial cells and use the host's ribosomes for replication.
• C. They use reverse transcriptase to convert their RNA genome into DNA, which integrates into the host genome.
• D. They replicate by budding from the host cell without altering the host's genetic material.

Answer: (C)

Verified step by step guidance

1. Understand the nature of retroviruses: Retroviruses are a group of RNA viruses that have a unique replication cycle involving reverse transcription.
2. Recall that retroviruses carry an enzyme called reverse transcriptase, which allows them to convert their RNA genome into complementary DNA (cDNA).
3. Recognize that this cDNA is then integrated into the host cell's genome, allowing the virus to use the host's cellular machinery to produce viral proteins and new viral particles.
4. Eliminate incorrect options by noting that retroviruses do not directly translate RNA into proteins without a DNA intermediate, nor do they infect bacterial cells (which are targeted by bacteriophages), and they do alter the host genome rather than just budding without integration.
5. Conclude that the best description of retrovirus action is their use of reverse transcriptase to convert RNA into DNA, which integrates into the host genome.