Metabolism of RNA phosphorus in Escherichia coli infected with bacteriophage T7

Historical Development of the Concept of the Gene

“…Extending this ®nding, Volkin andAstrachan (1956a, 1956b) measured phosphorus incorporation into the RNA of different subcellular fractions of E. coli after phage infection. The remarkable ®nding was that the purine-pyrimidine base composition of the RNA of bacterial cells after T7 phage infection is signi®cantly different than that of E. coli ribosomal RNA and instead resembles more closely that of the T7 phage DNA, indicating that the RNA was virus speci®c (Volkin et al, 1958). Subsequently, Volkin (1960) measured a rapid turnover of RNA formed after infection, it having a short half-life of the order of a few minutes, and found that phage production would not occur in the absence of this fraction.…”

Deoxyribonucleic Acids

“…Supporting evidence, showso KIT ing that cells synthesize metabolically unstable polyribonucleotides with apparent nucleotide compositions which resemble that of DNA (100 to 103), and that the polyribonucleotides differ in sedimentation coefficients from transfer-RNA or ribosomal-RNA but combine reversibly with the ribo somes (99,104,105), has greatly stimulated recent research and led to the tentative acceptance of the central messenger-RNA concept. Interestingly enough, however, a more sophisticated second look has been followed by the modification or abandonment of some of the cardinal points on which the messenger-RNA hypothesis was founded.…”

Relations Between Mutations and Base Sequences in the Amino Acid Code

“…The average base composition of the "U-code" is 48% U and about 17% for each of A, C, and G, while the base composition of messenger RNA from various sources is 27-31% A, 15-24% C, 21-24% G, and 28-35.5% U.4' 30,31,41,42 The deviation of C: G from a 1.00 ratio may indicate that messenger RNA is the complement of only one of the two strands of DNA; this has been discussed elsewhere.6' 48…”

“…In terms of the U-rich code in Table 3, 42 transitional mutations and 92 transversional mutations can result from single-base changes that lead from one coding triplet to another. Twenty of these transitional mutations and 13 of these transversional mutations (excluding duplications) are in Table 2.…”