Tagged oliggonucleotides and their use in nucleic acid amplification methods

The present invention relates to a method for the selective amplification of at least one target nucleic acid sequence from a nucleic acid sample, said method comprising the steps of (a) treating a nucleic acid sample comprising a target nucleic acid sequence with a tagged oligonucleotide comprising first and second regions, said first region comprising a target hybridizing sequence which hybridizes to a 3'-end of said target nucleic acid sequence and said second region comprising a tag sequence situated 5' to said target hybridizing sequence, wherein said second region does not stably hybridize to a target nucleic acid containing said target nucleic acid sequence; (b)reducing in said nucleic acid sample the effective concentration of unhybridized tagged oligonucleotide having an active form in which a target hybridizing sequence of said unhybridized tagged oligonucleotide is available for hybridization to said target nucleic acid sequence; and (c) producing amplification products in a nucleic acid amplification reaction using first and second oligonucleotides, wherein said first oligonucleotide comprises a hybridizing sequence which hybridizes to a 3'-end of the complement of said target nucleic acid sequence and said second oligonucleotide comprises a hybridizing sequence which hybridizes to the complement of said tag sequence, wherein said second oligonucleotide does stably hybridize to a target nucleic acid containing said target nucleic acid sequence, wherein each of said amplification products comprises a base sequence which is substantially identical or complementary to the base sequence of said target nucleic acid sequence and further comprises a base sequence which is substantially identical or complementary to all or a portion of said tag sequence, and wherein step (b) comprises inactivating unhybridized tagged oligonucleotide so that said unhybridized tagged oligonucleotide does not stably hybridize to said target nucleic acid sequence during step (c).