Fractionated strands of bacterial deoxyribonucleic acid. 3. Transformation efficiencies and rates of phenotypic expression.

Preferential binding of guanine-rich ribopolymers to one of the complementary strands of denatured deoxyribonucleic acid (DNA) of Diplococcus pneumoniae permitted the fractionation of the complements in CsCl density gradients. Phenotypic expression of the newly acquired genes for four drug resistances was more rapid in cells transformed by the heavy fractions than in those transformed either by light fractions or by unfractionated DNA. The efficiencies of transformation with the two complements were nearly equal for the four markers tested. Both efficiency and expression results were the same whether we assayed the residual activity or the activity obtained by annealing the fractions with excess recipient DNA.