I started by creating a color-coded chart that listed all seven classes, organizing them by type of genetic material (like dsDNA, ssDNA, dsRNA, etc.) and noting where in the cell they replicate (nucleus or cytoplasm). What helped most with the (+)-sense vs. (-)-sense ssRNA viruses was thinking of the (+)-sense RNA as already being like mRNA—so the host ribosomes can immediately translate it into proteins. In contrast, the (-)-sense RNA is like a mirror image; it first needs to be converted to (+)-sense RNA by an RNA-dependent RNA polymerase before it can be translated. That clicked for me when I thought of (+) as ready-to-use and (-) as needing a translator.
For examples, I used Class IV for (+)-sense ssRNA viruses like Poliovirus, and Class V for (-)-sense ssRNA viruses like Influenza. And to connect this to replication strategies, I’d explain how the virus’s genetic material dictates whether it brings its own enzymes or relies on the host—RNA viruses usually carry or code for their own polymerases because host cells don’t naturally replicate RNA from RNA.
When it came to the critical thinking questions, I found it helpful to frame the Baltimore classification as a roadmap for understanding how a virus hijacks the host. It’s not just about the genome—it’s about how that genome shapes the virus’s behavior, its vulnerabilities, and even how we might target it with therapies.
Hope this helps clarify things!