Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 133

There are more different types of (+) strand RNA viruses than any other, and 38 families have been recognized [not counting (+) strand RNA viruses with DNA intermediates]. These genomes are linear and may be single molecules (non-segmented) or segmented, depending on the family. The families Arteriviridae, Astroviridae, Caliciviridae, Coronaviridae, Flaviviridae, Hepeviridae, Nodaviridae, Picornaviridae, and Togaviridae include viruses that infect vertebrates. (+) strand RNA genomes usually can be translated directly into protein by host ribosomes. The genome is replicated in two steps. The (+) strand genome is first copied into a full-length (–) strand, and the (–) strand is then copied into full-length (+) strand genomes. In some cases, a subgenomic mRNA is produced.