422 R. M. S. SMELLIE 



extent in the reactions in the infected cell. From these observations and 

 results obtained with phage inactivated by exposure to ultraviolet and 

 X-irradiation and also from systems infected with both Te and T7 phage, 

 it appears that much of the parent material appearing in the progeny is 

 derived from breakdown products of the parent phage in the medium, and 

 that there is little transfer of genetic units from parent phage to progeny. 



Similar experiments carried out with T2r"^, T4r, and T3 phages labeled 

 with P32 and C'^ by Watson and Maaloe'^^ indicated that about 45% of 

 the parent isotope was incorporated in the progeny, 5 to 10 % was associated 

 with bacterial debris, and the remainder was in the nonsedimentable frac- 

 tion. It was found that the transmission of P^- from the parent phage to 

 progeny occurred mainly in the early formed phage and that the subsequent 

 particles received little isotope from the parent. 



Hershey and Chase,^®- using T2 phage labeled with P^- and S^^, observed 

 that on infection most of the phage DNA enters the infected cell while a 

 residue, containing most of the phage sulfur-containing protein, remains 

 attached to the surface of the infected cell. 



In a later paper Hershey^^^ has followed the synthesis of T2 bacteriophage 

 in P^--labeled systems. He concludes that on infection a pool of precursor 

 DNA is built up which is subsequently incorporated into the phage par- 

 ticles. The kinetics of transport of phosphorus from the culture medium, 

 bacterial DNA, and infecting phage DNA to the viral progeny have been 

 studied, and it has been noted that the phosphorus of the mature phage 

 does not exchange with that in the precursor. See also p. 460. 



The S. muscae bacteriophage system has been investigated by Price, ^^'^ 

 who has found that in certain circumstances absorption of the virus par- 

 ticles kills the bacterial cells, no virus material being synthesized. In certain 

 strains of S. muscae, phage particles are released before lysis occurs, while 

 in other strains cellular lysis and release of virus particles occur simultane- 

 ously. 



VII. The Catabolism of the Nucleic Acids 

 1. General 



Ingested nucleic acids are broken down in the intestine under the in- 

 fluence of the enzymes already discussed in Chapter 15 and recently re- 

 viewed by Christman,^^ Davidson,**''^*^ and Laskowski,'^*' yielding free 

 bases, phosphoric acid, and the free sugar. 



1" J. D. Watson and O. Maaloe, Biochem. et Biophtjs. Acta 10, 432 (1953). 

 1" A. D. Hershey and M. Chase, J. Gen. Physiol. 36, 39 (1952). 

 '«3 A. D. Hershey, J. Gen. Physiol. 37, 1 (1953). 

 '«■' W. H. Price, '/. Gen. Physiol. 35, 409 (1952). 

 '66 J. N. Davidson, Brit. Med. Bull. 9, 154 (1953). 



166 M. Laskowski, in "The Enzymes" (Sumner and Myrback, eds.), Vol. 1, Part 2, 

 p. 956. Academic Press, New York, 1951. 



