Which of the following characterizes bacteriophages (phages) but not viruses that infect eukaryotes?

• A. They replicate exclusively in the cytoplasm of the host cell.
• B. They infect cells by endocytosis.
• C. They inject their genetic material into the host cell through a tail structure.
• D. They possess a lipid envelope derived from the host cell membrane.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the nature of bacteriophages (phages) and how they differ from viruses that infect eukaryotic cells. Bacteriophages specifically infect bacteria, while eukaryotic viruses infect eukaryotic cells.
2. Step 2: Review the replication sites of viruses. Many eukaryotic viruses replicate in the cytoplasm or nucleus, but bacteriophages typically inject their genetic material into the bacterial cytoplasm without entering the whole cell.
3. Step 3: Examine the entry mechanisms. Eukaryotic viruses often enter host cells by endocytosis or membrane fusion, whereas bacteriophages use a specialized tail structure to inject their DNA or RNA directly into the bacterial cell.
4. Step 4: Consider the presence of lipid envelopes. Many eukaryotic viruses have lipid envelopes derived from the host cell membrane, but bacteriophages generally lack such envelopes and have protein-based capsids and tail structures.
5. Step 5: Conclude that the unique characteristic of bacteriophages is their method of infecting host cells by injecting genetic material through a tail structure, which is not seen in viruses that infect eukaryotic cells.