Studies on Polynucleotides

Abstract The incorporation of ribonucleotides into DNA catalyzed by Escherichia coli DNA polymerase I in the presence of Mn++ has been studied with two synthetic DNA's of defined sequence. In general agreement with the findings of Berg et al. ((1963) in Symposium on Informational Macromolecules, p. 467, Academic Press, New York), CMP and GMP could be incorporated at rates comparable to their deoxy analogs. AMP was incorporated only slowly and UMP was not incorporated at all. In studies of the fidelity of incorporation, misincorporation was observed at 37° in the presence of both GTP and CTP. The misincorporation was also observed at 10° in the presence of GTP but not in the presence of CTP. The sequence G-G was found to slow down subsequent nucleotide incorporation in the presence of GTP. The DNA's containing CMP or GMP were selectively cleaved by alkali or specific ribonucleases and expected products were thus obtained.