Universal tag assay

The present invention disclosure provides methods and compositions for a universal tag assay wherein a universal detector having detection probes is incubated with tagged molecules having identifier tags corresponding to targets, and hybridization of an identifier tag to a complementary detection probe indicates the presence of the corresponding target in the material being assayed. In particular, the invention disclosure provides methods and compositions for detecting target nucleotide sequences in a sample by target-dependent manipulations that generate tagged molecules having identifier tags corresponding to target nucleotide sequence, where incubation of tagged molecules with a universal detector having detection probes permits hybridization of identifier tags to complementary detection probes, thereby indicating the presence of the target nucleotide sequence corresponding to each identifier tag. Preferred embodiments include use of the universal tag assay for detecting variant sequences including single nucleotide polymorphisms (SNPs), allelic variants, and splice variants. Preferred embodiments further include the use of ruthenium amperometry to detect hybridization of tagged DNA or RNA molecules to detection probes immobilized on a universal detector, preferably a universal chip having gold or carbon electrodes.