Virus polyhedral structures

II A radically different type of nucleoprotein is that provided by the smaller RNA viruses of the elongated spiral type like tobacco mosaic, or of the polyhedral type such as tomato bushy stunt, tipula virus or poliomyelitis virus. The only one of these adequately studied has been tobacco mosaic virus, Franklin [19, 20], and here it appears that the protein and not the nucleic acid determines the structure. There is only one RNA chain and this is wound helically so that one protein is in contact with three successive nucleotides. 

FIGURE 2.6 Structural shapes of viruses (a) helical, (b) polyhedral, and (c) combination T-even. 

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