.'!.). NUCLEIC ACIDS OF THE BACTERIAL VIRUSES 



2 4 DAYS 8 10 14 20 



100- 



199 



2 04 06 



FRACTION OF P 32 ATOMS OECAYED 



Fig. 2. Percentage of parental P 32 contained in first generation progeny trans- 

 ferable to the second generation progeny as a function of the fraction of P 32 atoms 

 decayed. The solid line is the transfer expected if, of the P 32 in the first generation 

 progeny, 60% is in pieces of 15% each of the original DNA, while the remainder (40%) 

 is in pieces of 0.3% each of the original DNA. [From G. S. Stent, G. H. Sato, and N. 

 K. Jerne, J. Mol. Biol. 1, 134 (1959).] 



intact is supported by the fact that supplying infected cells with large 

 amounts of DXA precursors such as thymidine or uridine cannot reduce the 

 transfer of C 14 from parent to progeny thymidine. 61 



(4) Possibility of Artifact. These experiments taken together present 

 a harmonious picture of physically and functionally bipartite DXA in the 

 T-even phages. With some allowance for numerical divergencies they sug- 

 gest that there is in a T-even phage particle one large molecule of DXA 

 (comprising some 30-50% of the total content) which in normal replication 

 divides into two pieces which in future generations preserve their integrity. 

 If irradiated by ultraviolet light, this piece can be irreparably damaged, 

 but can be, in a mixed infection with live phage, incorporated into a progeny 

 particle. 



The remainder of the DXA appears to be very extensively degraded dur- 



