Principles of Virology, Volume 1. Jane Flint

Principles of Virology, Volume 1 - Jane Flint


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alt="image"/> Adenoviridae Orthomyxoviridae Papillomaviridae Polyomaviridae Retroviridae 7, 887, 8810 1, 215, 1623, 2429, 30 RNA editing image Paramyxoviridae Filoviridae Hepatitis delta virus 6, 888 Information on both strands image Adenoviridae Polyomaviridae Retroviridae 7-97-910 1, 223, 2429, 30 Polyproteinsynthesis image AlphavirusesFlaviviridae Picornaviridae Retroviridae 6, 116, 116, 116, 11 33, 349, 1021, 2229, 30 Leaky scanning image Orthomyxoviridae Paramyxoviridae Polyomaviridae Retroviridae 11111111 15, 1629, 30 Reinitiation image Orthomyxoviridae Herpesviridae 1111 15, 16 Suppression of termination image AlphavirusesRetroviridae 1111 33, 3429, 30 Ribosomalframeshifting image Astroviridae Coronaviridae Retroviridae 111111 5, 629, 30 IRES image Flaviviridae Picornaviridae 1111 21, 22 Nested mRNAs image Coronaviridae Arteriviridae 66 5, 65, 6

      Despite their utility, genome sequences cannot provide a complete understanding of how viruses reproduce. The genome sequence of a virus is at best a biological “parts list”: it provides some information about the intrinsic properties of a virus (for example, predicted sequences of viral proteins and particle composition), but says little or nothing about how the virus interacts with cells, hosts, and populations. This limitation is best illustrated by the results of environmental metagenomic analyses, which reveal that the number of viruses around us (especially in the sea) is astronomical. Most are uncharacterized and, because their hosts are also unknown, cannot be investigated. A reductionist study of individual components in isolation provides few answers. Although the reductionist approach is often the simplest experimentally, it is also important to understand how the genome behaves among others (population biology) and how the genome changes with time (evolution). Nevertheless, reductionism has provided much-needed detailed information for tractable virus-host systems. These systems allow genetic and biochemical analyses and provide models of infection in vivo and in cells in culture. Unfortunately, viruses and hosts that are difficult or impossible to manipulate in the laboratory remain understudied or ignored.

      All viruses with genome sizes spanning the range from the biggest to the smallest are successful as they continue to reproduce and spread within their hosts. Despite detailed analyses, there is no evidence that one size is more advantageous than another. All viral genomes have evolved under relentless selection, so extremes of size must provide particular advantages. One feature distinguishing large genomes from smaller ones is the presence of many genes that encode proteins for viral genome replication, nucleic acid metabolism, and countering host defense systems. When mimiviruses were first discovered, the surprise was that their genomes encoded components of the protein synthesis


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