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Positive-strand RNA viruses (+ssRNA viruses) are a group of related viruses that have positive-sense, single-stranded genomes made of ribonucleic acid. The positive-sense genome can act as messenger RNA (mRNA) and can be directly translated into viral proteins by the host cell's ribosomes .
Bunyaviruses have three single-stranded RNA (ssRNA) fragments, some of them containing both positive-sense and negative-sense sections; arenaviruses are also ssRNA viruses with an ambisense genome, as they have three fragments that are mainly negative-sense except for part of the 5′ ends of the large and small segments of their genome.
The fourth Baltimore group contains viruses that have a positive sense single-stranded RNA (+ssRNA) genome. For +ssRNA viruses, the genome functions as mRNA, so no transcription is required for translation. +ssRNA viruses will also, however, produce positive sense copies of the genome from negative sense strands of an intermediate dsRNA genome.
Negative-sense ssRNA viruses (Group V) must have their genome copied by an RNA replicase to form positive-sense RNA. This means that the virus must bring along with it the enzyme RNA replicase. The positive-sense RNA molecule then acts as viral mRNA, which is translated into proteins by the host ribosomes.
Another case study described a 25-year-old man from Nevada who tested positive for SARS‑CoV‑2 on 18 April 2020 and on 5 June 2020 (separated by two negative tests). Since genomic analyses showed significant genetic differences between the SARS‑CoV‑2 variant sampled on those two dates, the case study authors determined this was a ...
For +ssRNA viruses, an intermediate dsRNA genome is created from which +ssRNA is synthesized from the negative strand. [3] For -ssRNA viruses, genomes are synthesized from complementary positive sense strands. [5] dsRNA viruses replicate their genomes from mRNA by synthesizing a complementary negative sense strand to form genomic dsRNA. [4]
Genome type and replication cycle of different RNA viruses. RNA viruses in Orthornavirae typically do not encode many proteins, but most positive-sense, single-stranded (+ssRNA) viruses and some double-stranded RNA (dsRNA) viruses encode a major capsid protein that has a single jelly roll fold, so named because the folded structure of the protein contains a structure that resembles a jelly ...
The genome is a single-stranded positive-sense RNA (+ssRNA) genome that is about 7500 nucleotides long. [2] The viral particle is about 30 nm in diameter with icosahedral symmetry . Because of its short genome and its simple composition—only a strand of RNA and a nonenveloped icosahedral protein coat encapsulating it—poliovirus is widely ...