RNA-DNA hybridization in solution without DNA reannealing

In solutions containing 70% formamide hybridization of RNA to denatured DNA proceeded in the absence of DNA reannealing at temperatures permitting the optimum rate of formation of RNA-DNA hybrids. At low complementary DNA to RNA ratios the percentage of E. coli ribosomal RNA hybridized was substantially higher in 70% formamide than in solutions lacking formamide. The ability to perform RNA-DNA hybridization without competing DNA reannealing facilitates the description of the kinetics and stoichiometry of the reaction.