Which statement best describes the poliovirus genome and its expression strategy?

• A. The genome contains multiple segmented RNAs
• B. A single open reading frame encodes a polyprotein that is cleaved into functional proteins
• C. The genome is single-stranded DNA
• D. The genome encodes individual proteins from separate reading frames

Answer: (B)

The main idea is how poliovirus uses its genome to make all of its proteins. The virus has a positive-sense, single-stranded RNA genome that can function directly as mRNA in the host cell. It contains a single long open reading frame that is translated into one giant polyprotein. This polyprotein is then cut by viral proteases into the individual functional proteins needed for the virus—structural proteins that form the capsid and nonstructural proteins that drive replication and processing. The translation is directed by an internal ribosome entry site in the 5' untranslated region, not by a cap structure, and there is no segmented genome or separate reading frames producing independent proteins. This combination—one ORF, polyprotein expression, and subsequent proteolytic processing—defines how poliovirus expresses its genes.