Use of DNA polymerase I primed by a synthetic oligonucleotide to determine a nucleotide sequence in phage fl DNA.

A sequence of 50 residues in f1 DNA has been determined by the extension of a chemically synthesized octadeoxyribonucleotide by Escherichia coli DNA polymerase I, with radioactive nucleoside triphosphates and f1 DNA template. The polymerized product was synthesized either in the presence of manganese and a mixture of ribo- and deoxyribotriphosphates or in a magnesium-containing reaction with one or more of the four triphosphates absent. The sequence determination depended largely on fractionation of the polymerized products by two-dimensional "homochromatography." This approach and the techniques for the subsequent sequence analysis should be of general use for determining other sequences of DNA. Several features of this sequence suggest that it is located in an intercistronic region of f1 DNA.