RNA-DNA hybridization: demonstration in a mammalian system of competition by preincubation.

Nonspecific intermolecular interactions obscure the interpretation of competition experiments involving hybridization of DNA and RNA in mammalian systems when the labeled RNA/DNA ratio is low. The effect of these interactions can be minimized by choosing a sufficiently high ratio of labeled RNA/DNA. No serious effect of nonspecific interactions is observed in bacteriophage systems, even at very low labeled RNA/DNA ratios.