I 9 f. 2 |. D. W ATS ON 



was measured. Riley, Pardee, Jacob, and Monod 31 obtained the striking 

 finding that 0-galaCtOsidase, genetically determined by a specific male gene, 

 began to be synthesized at its maximum rate within several minutes after 

 gene transfer. Thus the steady state number of /^-galactosidase templates was 

 achieved almost immediately. Conversely when the /:. colt chromosome was 

 inactivated bv decay of 32 P atoms incorporated into DNA, they observed 

 that active enzyme formation stops within several minutes. It thus appeared 

 that the ribosomal templates could not function without concomitant DNA 

 function. 



At the same time, Francois Gros discovered 32 that bacteria grown in 5- 

 fluorouracil produced abnormal proteins, most likely altered in amino acid 

 sequences. s-Fluorouracil is readily incorporated into bacterial RNA and its 

 presence m RNA templates may drastically raise the mistake level. More 

 unexpected was the observation that following 5-fluorouracil addition the 

 production of all normal proteins ceases within several minutes. Again this 

 argues against the persistance of any stable templates. 



Unstable RNA Molecules in Phage Infected Cells 



At first it was thought that no RNA synthesis occurred in T2 infected cells. 

 But in 1952 Hershcy 33 observed that new RNA molecules are synthesized at 

 a rapid rate. But no net accumulation occurs since there is a correspondingly 

 last breakdown. Surprisingly almost everybody ignored this discovery. This 

 oversight was partly due to the tendency, still then prevalent, to suspect that 

 the metabolism of virus infected cells might be qualitatively different from 

 that of uninfected cells. 



Volkm and Astrachan 34 were the first (1956) to treat Hershcy's unstable 

 fraction seriously. They measured its base composition and found it different 

 from that of uninfected E. coli cells. It bore a great resemblance to the infect- 

 ing viral DNA which suggested that it was synthesized on T2 DNA tem- 

 plates. Moreover, and most importantly, this RNA fraction must be the tem- 

 plate for phage specific proteins. Unless we assume that RNA is not involved 

 in phage protein synthesis, it necessarily follows that the Volkin-Astrachan 

 DNA-like RNA provides the information for determining amino acid se- 

 quences in phage specific proteins. 



Not till the late summer of 1959 was its physical form investigated. Then 

 Nomura, Hall, and Spicgelman 35 examined its relationship to the already 



s-122 



