Exonuclease cycling assay: an amplified assay for the detection of specific DNA sequences.

An assay is described in which an oligonucleotide probe is specifically digested by lambda exonuclease only when it is annealed to its complementary sequence. In this assay, a cycling effect occurs whereby a small amount of target sequence acts as a specific co-factor in the enzymatic degradation of a larger number of molecules of an oligonucleotide probe. This amplification principle is demonstrated and the effect of the oligonucleotide probe sequence investigated. The necessary steps needed to convert this effect into a useful diagnostic tool are discussed.