94 



Martynas YCas 



difference of one or two residues from the statistically expected value produces 

 very large relative deviations. 



Since the frequency of occurrence of an individual amino acid is small, 

 even a larger protein such as hemoglobin may be too small to be a statistically 

 valid sample for the purpose of calculating frequencies on the basis of a random 

 RNA sequence. The following case is of interest. The RNA's of liver and of 

 reticulocytes are virtually identical in composition, and therefore the proteins 

 (bulk liver protein and hemoglobin) would be expected to have a very similar 

 composition. Actually, this is not the case (Fig. 6). Considerable differences 



4 6 8 



LIVER PROTEIN 



Fig. 6. The composition of bulk liver protein (142) and hemoglobin (93). The 

 RNA composition of liver from (89) of reticulocytes (143). All in moles per cent. 



exist, as can be seen from the deviations of the points from the line of slope 1 . 

 It would be better to use for this purpose the bulk RNA's and proteins of 

 whole organisms and organs, were it not for the fact that bulk protein and RNA 

 from various sources is so similar that no strong check on the coding principle 

 is possible. 



The method of assignments from the assumption of a random RNA sequence 

 fails, then, either strongly to confirm or to deny any proposed coding principle. 



It is possible that as more information becomes available some light may 

 be thrown on the coding problem from a study of replacements of residues in 

 homologous proteins, if replacements prove to be nonrandom. 



The reader will not fail to notice that the inadequacy of the data render 

 most of my conclusions tentative. More information of the type considered 



