CHEMICAL COMPOSITION 91 



Studying transfer of host cell pyrimidines to phage T6, isolated 

 thymidylic acid, deoxycytidylic acid, and adenine from the 

 phage. Smith and Wyatt (1951) reported the presence of ade- 

 nine, guanine, cytosine, and thymine in both T5 and T2. 

 Marshak (1951) found adenine, guanine, and thymine in phage 

 T2 but made the rather startling observation that neither cytosine 

 nor 5-methylcytosine could be found, although cytosine was 

 present in phage T3. Marshak also noted that the absorption 

 spectrum for the guanine isolated from phage T2 was abnormal 

 suggesting the possibility of contamination of the guanine with 

 some other base. The confusion was finally resolved by Wyatt 

 and Cohen (1953) who reported that phages T2, T4, and T6 

 contain neither cytosine nor 5-methylcytosine, but contain in- 

 stead a new base, 5-(hydroxymethyl)cytosine. Some analyses on 

 the nucleic acids of phages are given in Table X. A few addi- 

 tional data are given by Lwoff (1953). It appears that only T2, 

 T4, and T6 contain 5-(hydroxymethyl)cytosine. 



TABLE X 

 The Molar Proportions of Nucleic Acid Bases in Phages 



« Smith and Wyatt (1951). 



* Marshak (1951), absolute values arbitrary. 



'Wyatt and Cohen (1953). 



^ Koch, Putnam, and Evans (1952), absolute values arbitrary. 



' Hershey, Dixon, and Chase (1953). 



•'^ Lunan and Sinsheimer (1956). 



" 5-(Hydroxymethyl) cytosine. 



The presence of glucose in glucosidic linkage with 5-(hydroxy- 

 methyl) cytosine (HMC) of T2, T4, and T6 is clearly indicated 



