124 Information Storage and Neural Control 



and the ability to make this phage is transmitted as a heritable 

 property of the cell. Temperate phage infections may lead to 

 either of these results; intemperate phages can only cause the 

 lytic response. We shall be concerned mainly with describing the 

 synthetic capacities of cells undergoing the lytic response to infec- 

 tion by the intemperate T-even series of phages. 



The entry into the cell of the DNA from such a phage brings 

 about immediate and dramatic changes in synthetic events within 

 the cell. Cellular DNA, RNA, and protein syntheses seem to be 

 stopped immediately and no further cell division takes place (2). 

 The DNA of the cell is digested by a DNAse and contributes 

 nucleotides to phage DNA (3, 4, 5). Although many enzymes and 

 metabolic pathways within the cell are able to function (2), the 

 integration of events which previously led to cellular macro- 

 molecular synthesis and continued cell growth is disrupted. Recent 

 experiments from several different laboratories (6) offer a reason- 

 able explanation of the subsequent events in the course of synthesis 

 ol new phage particles. 



An outline of the new work is best begun by describing the 

 concept of messenger RNA as it functions in phage infection. 

 Current ideas of the genetic control of protein synthesis delegate 

 to DNA the role of carrier of genetic information. The structural 

 site of protein formation has been shown to be the ribosome (7, 8), 

 which, however, is composed of RNA and protein (9). Thus, it 

 has been presumed that some RNA molecule probably served to 

 transport information from the DNA to the ribosome. The first 

 evidence of such an RNA was obtained by Volkin and Astrachan 

 (10), who found in phage-infected cells that just after infection 

 a species of RNA was formed which had base ratios (substituting 

 uracil for thymine and cytosine for 5-hydroxymethylcytosine) 

 similar to those of infecting phage DNA. Ribosomal RNA does 

 not bear such a relationship to DNA (11). It has since been shown 

 that this newly fornied RNA is linked to ribosomes, which form 

 phage proteins, but is not the ribosomal RNA itself (12, 13). 

 Hall and Spiegelman (14) have performed a critical test of the 

 source of this RNA by demonstrating that it can combine phys- 

 ically by hydrogen bonding with phage DNA, which directed its 

 formation, but not with any other DNA. Thus, one concludes 



