ERWIN CHARGAFF 



TABLE VII 

 Examples of Pleromeric Relationships in Deoxyribonucleic Acids 



Pleromers 



Molar ratios 



Source 



of 

 DNA 



Analogue or 



natural 



satellite 



(mole %) 



Normal 

 pvrimidine 

 (mole %) 



Comple- 



mentariness 



ratio* 



6 Am/ Refer- 

 6Kt ence 



Wheat 5 -Methyl- 5-9 Cytosinei6-8 

 germ cytosine 



096 



1-03 



38 



* In the case of 6-aminopyrimidines (cytosine, 5-methylcytosine), this is the 

 molar ratio of guanine to the sum of 6-aminopyrimidines; in the case of the 

 halopyrimidines, the complementariness ratio is the molar ratio of adenine to the 

 sum of 6-keto pyrimidines. 



t Molar ratio of 6-amino nucleotides to 6-keto nucleotides. 



% N-Methyladenine (1-4 mole "^^o) omitted from the calculations. 



evident with respect to the amino acid sequence in proteins than to the 

 nucleotide arrangement in nucleic acids. More and more instances of such 

 homotopic relationships are being revealed as knowledge on specific 

 sequences in proteins increases. As concerns the deoxyribonucleic acids, 

 we are largely limited to the consideration of simple sequences, such as 

 purine-pyrimidine-purine, or of small bunches of pyrimidine nucleotides. 

 The development of the study of larger clusters, mentioned before, will 

 doubtless contribute much to our knowledge. I have emphasized above a 

 possible instance of homotopy, namely, the remarkable similarity in distri- 

 bution, as solitary nucleotides, of the two 5-methyl pyrimidines (thymine 

 and 5-methylcytosine) in rye germ deoxyribonucleic acid [37]. Examples 

 of the absence of homotopic relationships, where they would have been 

 expected, are more numerous: cytosine and 5-methylcytosine, e.g. in rye 



