1. The following abbreviations are used: tRNA—transfer (soluble) ribonucleic acid; A, G, U, C, T—the five common bases; I—hypoxanthine; ψU—pseudouridine; 5-met-C—5-methyl-cytosine; A–U and G–C—the Watson–Crick base pairs; PNPase—polynucleotide phosphorylase; TMV—tobacco mosaic virus.
2. Crick, F. H. C., Symp. Soc. Exp. Biol., 12, 25 (1957).
3. Hoagland, M. B., Brookhaven Symp. Biol., 12, 40 (1959).
4. Brown, G. L., Prog. Nucleic Acid Res., 2, 259 (1963). Luborsky, S. W., and Cantoni, G. L., Biochim. Biophys. Acta, 61, 481 (1962).
5. Fresco, J. R., Alberts, B., and Doty, P., Nature, 188, 98 (1960).