Many RNA viruses with a positive sense strand do not need to contain a virion associated polymerase. The RNA can serve as a mRNA to make polymerases upon cell entry. RNA viruses with a negative sense strand must contain a virion associated polymerase to make positive sense strand RNA upon cell entry. The replication strategy of the virus depends on the nature of its genome. Some replicate in the nucleus e.g adenoviruses using cellular proteins.
Poxviruses replicate in the cytoplasm and make their own enzymes for nucleic acid replication.
These viruses have segmented genomes. Each genome segment is transcribed separately to produce monocistronic mRNAs. Translation results in the formation of a polyprotein product, which is subsequently cleaved to form the mature proteins. Complex Transcription e.g. Togaviruses. Segmented e.g. Orthomyxoviruses.