Which description correctly characterizes the poliovirus genome and basic structure?

• A. Non-enveloped, icosahedral capsid; positive-sense single-stranded RNA genome (~7.5 kb) with a single open reading frame encoding a polyprotein
• B. Enveloped, helical capsid; negative-sense RNA genome
• C. Enveloped, icosahedral; positive-sense RNA genome
• D. Non-enveloped, icosahedral; double-stranded DNA genome

Answer: (A)

Poliovirus is a small, non-enveloped virus with an icosahedral capsid belonging to the picornaviruses. Its genome is a positive-sense single-stranded RNA about 7.5 kilobases long, and it contains a single long open reading frame that is translated into one polyprotein, which is then cleaved into structural and nonstructural proteins. Because the genome is positive-sense RNA, it can act directly as mRNA in the host cell to produce the polyprotein. The genome is not segmented and there is no lipid envelope surrounding the capsid, which matches the description of being non-enveloped with an icosahedral capsid and a positive-sense RNA genome of ~7.5 kb with a single ORF encoding a polyprotein.