Medical Pharmacology Chapter 37: Antiviral Drugs
Viral Gene Expression and Viral Replication: Baltimore Classification System
Viral genomes can be categorized as belonging to one of seven groups, dependent on pathways leading to mRNA and directed protein synthesis.1
This grouping is the Baltimore classification system.1
The system highlights differing RNA polymerases required by viruses associated with each group.
Sometimes the polymerase enzyme is available natively in the cell and in other circumstances must be made available by the virus.
Single-stranded RNA viral genomes are subcategorized into two groups.
Viruses in one group package the "sense" RNA strand which support direct translation into viral proteins.
This strand, as disucssed earlier, is described as the positive (or plus) strand.
However, other viruses package the "antisense" strand which only provides a complimentary copy code for viral proteins and is therefore not directly transcribable.
This latter group is described therefore as a negative (or minus) strand. On this basis the details of the Baltimore classification system can be described.1
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