Viral RNA genomes

 

• Can be single-stranded (ss) or double-stranded (ds) and can occur as a single or fragmented molecule
• If the ss sense or polarity is the same as mRNA is said to be positive or positive plus
• If the ss sense or polarity is complementary to mRNA is said to be a negative or minus sense
• Cells have no RNA‐dependent RNA polymerase (RdRp)RNA virus genomes encode RdRp for transcribing RNA and replicating the genome
• mRNA is readable by ribosomes
• The ssRNA viral genome varies from 1.7 kb to 33 kb and that of ds RNA viruses from 7 to 27 kbp
• The RNA genomes have one or more open reading frames (ORFs) that encode the viral proteins. But there are also regions of RNA that do not code for protein.
• These non-coding regions (NCRs) or untranslated regions (UTRs) are often highly conserved within a virus family, indicating that they have important functions.
• All RNA genomes have NCRs at their 5′ and 3′ ends.