20 VIRUSES, RICKETTSIAE AND BACTERIA 



Material Present Virus 



RNA "| 



DNA ^ Polyhedral virus 



Protein J 



Tobacco mosaic virus 



RNA \ 



Protein j 



RNA ? 



Thus the analysis of the vaccinia virus shows the presence of 

 proteins, DNA, neutral fat, phospholipid, cholesterol, biotin, 

 flavine, copper and various as yet unidentified substances. The 

 Lee influenza virus has about 5% of its weight as a complex 

 polysaccharide containing mannose, galactose and glucosamine. 

 It is also becoming clear that the term " nucleic acid " should be 

 used with care since there are many different nucleic acids, and as 

 ChargafT (1957) points out, often the term " ribose nucleic acid " 

 is used when there is no evidence that the sugar ribose is present. 

 The precise structure of the nucleoproteins is not yet known, i.e. 

 the type of proteins, and the way in which the nucleic acid is 

 attached to the protein have yet to be fully elucidated, but some 

 evidence is available concerning the component nucleotides in the 

 nucleic acids of the virus. The table below, taken from Fruton 

 and Simmons (1958) indicates that the proportional composition 

 of the nucleotides varies in the different viruses. 



Virus Molar proportions in nucleic acid 



Adenylic Guanylic Cytidylic Uridylic 

 acid acid acid acid 



Tobacco mosaic virus 1-0 0-89 0-65 0-88 



Cucumber mosaic virus 1-0 1-0 0-75 1-15 

 Tomato bushy stunt 



virus 1-0 10 0-74 0-89 

 Turnip yellow mosaic 



virus 1-0 0-76 1-68 0-98 



This gives some hint of the complexity of nucleic acid, and 

 nucleoprotein structure, and makes one careful when ascribing 

 simplicity to a system that is not yet adequatel)' understood. 



