GED Science TestLife ScienceHard
A medical researcher is investigating a new drug designed to inhibit viral replication. The drug specifically targets the enzymes responsible for synthesizing viral DNA from an RNA template. This drug would be most effective against which type of virus?
- ARetroviruses (e.g., HIV)
- BRNA viruses that replicate directly (e.g., Poliovirus)
- CDNA viruses (e.g., Herpesvirus)
- DBacteriophages (viruses that infect bacteria)
Show answer & explanationAnswer & explanation
Correct answer: A. Retroviruses (e.g., HIV)
The drug targets enzymes that synthesize DNA from an RNA template. This process is called reverse transcription and is characteristic of retroviruses like HIV. DNA viruses replicate using DNA, and most RNA viruses replicate RNA directly from an RNA template.
Why the other options are wrong
- B. RNA viruses that replicate directly (positive-sense RNA viruses) use their RNA genome as mRNA to produce proteins, including RNA-dependent RNA polymerase, which replicates RNA from an RNA template, not DNA from an RNA template.
- C. DNA viruses replicate DNA from a DNA template, not RNA. The drug would not target their replication enzymes effectively.
- D. Bacteriophages are diverse; some are DNA, some RNA. However, the specific mechanism of synthesizing DNA from an RNA template is not a universal feature of bacteriophages, nor their defining replication strategy targeted by this drug.
Retroviral Replication
The unique replication strategy of retroviruses, which involves using an enzyme called reverse transcriptase to synthesize DNA from their RNA genome, before integrating this DNA into the host cell's genome.
- Genome: single-stranded RNA.
- Key enzyme: reverse transcriptase.
- Converts RNA to DNA (reverse transcription).
- Integrated DNA (provirus) then transcribed into new viral RNA.
Memory trick: RNA to DNA is a Retro-Reverse Revolution!