146 NUCLEOTIDE SEQUENCE IN DEOXYRIBONUCLEIC ACIDS 



TABLE 34 



FREQUENCY OF SOLITARY AND COUPLED PYRIMIDINE NUCLEOTIDE UNITS IN 



DEOXYRIBONUCLEIC ACID OF A THYMINE AUXOTROPH OF E. CoU t-arg" 



IN THE ABSENCE AND PRESENCE OF 5-BROMOURACIL* 



Growth supplements: 

 DNA Prep. No.: 



T + B 

 2 



Moles of pyrimidine per 

 100 gram-atoms of 

 DNA phosphorus 



Total T or B 



B/(T + B) • 100 in solitary units 

 B/(T + B) • 100 in coupled units 

 B/(T + B) • 100 in total DNA 



56 

 56 

 56 



* The nucleic acid preparations are numbered as in Table 32. The same 

 abbreviations as in Table 32 are used, with p indicating the number of 

 phosphate groups in the fragments having the general formula Py„p„+i 

 (Py = pyrimidine). No distinction is made between sequential isomers of 

 the coupled units. The figures are the averages of the results of two 

 separate hydrolysis experiments, each chromatographic component being 

 determined twice; the deviations from the averages are given in paren- 

 theses. This table is taken from a recent publication^o. 



acid specimens produced in the absence of the halopyrimidine 

 yielded at least eight distinct fractions, going from solitary units 

 to octanucleotide sequences, whereas with the preparations con- 

 taining 5-bromouracil the longest runs separated clearly were 

 those of five pyrimidines in a row. It may be that this often 

 observed difference is not without significance. 



