Final answer:
Positive single-stranded RNA (+ssRNA) can be directly translated into proteins, while negative single-stranded RNA (-ssRNA) needs to be converted to +ssRNA by RNA-dependent RNA polymerase (RdRP) before translation.
Step-by-step explanation:
Difference Between Positive and Negative Single-Stranded RNA
The difference between positive single-stranded RNA (+ssRNA) and negative single-stranded RNA (-ssRNA) lies in their functionality within a viral replication cycle. +ssRNA can be directly translated into viral proteins because it acts like cellular mRNA. In contrast, -ssRNA cannot be translated by host ribosomes until it is replicated into +ssRNA by viral RNA-dependent RNA polymerase (RdRP). This enzyme is crucial as it allows the negative strand to be used as a template to create positive-strand RNA, which can then be translated to produce viral proteins. For Group IV viruses with +ssRNA genomes, replicative dsRNA intermediates are formed during the replication process. Contrastingly, Group V viruses have -ssRNA genomes that are firstly transcribed into mRNA and then used to produce full-length positive RNA strands as templates for new negative genomes.
Positive single stranded RNA (+ssRNA) acts as messenger RNA (mRNA) and can be translated directly by the host ribosomes to make viral proteins. It has a positive polarity and can serve directly as mRNA without any additional steps.
In contrast, negative single stranded RNA (-ssRNA) has a negative polarity and cannot be translated by the host ribosomes. It needs to be replicated into positive single stranded RNA (+ssRNA) by viral RNA-dependent RNA polymerase (RdRP) before it can be translated. The RdRP converts the -ssRNA into +ssRNA, which can then be used as a template for protein synthesis.