RIBONUCLEIC acids (RNA) appear to play an important, if not critical, role in biosynthesis of macromolecules. In contrast to deoxyribonucleic acid (DNA) which is found solely in the nucleus, RNA is found primarily in the cytoplasm and in some manner appears to communicate the hereditary message of the chromosomes to the synthetic machinery of the cytoplasm. For this reason the elucidation of the mechanism of formation of RNA is of crucial importance in the understanding of cell physiology.
The class of substances grouped together under the generic term RNA as yet has not been resolved into constituents recognizable as individual molecular species. In spite of this difficulty, and of the fact that the structure and function of RNA still are not clearly established, a substantial body of information has been collected concerning biosynthetic pathways of RNA.
Early in the application of isotopic tracers, experiments with P32 (as inorganic phosphate)