A method of detecting a target nucleic acid sequence, comprising: a) providing a nucleic acid system, comprising: a. a downstream oligonucleotide probe, comprising at least 50 base pairs, having a sequence that is complementary to a first sequence of a target oligonucleotide and that has a cleavable sequence; and b. an upstream oligonucleotide primer, comprising at least 50 base pairs, having a sequence that is complementary to a second sequence of the target oligonucleotide and that has an initial nucleic acid polymerase binding site; b) denaturing DNA having the target sequence; c) hybridizing the upstream oligonucleotide primer and downstream oligonucleotide probe to the target oligonucleotide; d) binding a polymerase to the initial nucleic acid polymerase binding site; e) performing thermal cycling with a temperature range within 15°C of the Tm of the target nucleic acid sequence to extend the upstream oligonucleotide primer via polymerization with the polymerase toward the downstream oligonucleotide probe; f) cleaving nucleotides or small oligonucleotides of the downstream oligonucleotide probe;and g) detecting a signal resulting from said cleaving; wherein the downstream oligonucleotide probe is configured for a polymerase to cleave mononucleotides or small oligonucleotides at its 5' end, and wherein the Tm of the downstream oligonucleotide probe and the upstream oligonucleotide primer is within about 15°C of the target nucleic acid Tm. a) providing a nucleic acid system, comprising: a. a downstream oligonucleotide probe, comprising at least 50 base pairs, having a sequence that is complementary to a first sequence of a target oligonucleotide and that has a cleavable sequence; and b. an upstream oligonucleotide primer, comprising at least 50 base pairs, having a sequence that is complementary to a second sequence of the target oligonucleotide and that has an initial nucleic acid polymerase binding site; a. a downstream oligonucleotide probe, comprising at least 50 base pairs, having a sequence that is complementary to a first sequence of a target oligonucleotide and that has a cleavable sequence; and b. an upstream oligonucleotide primer, comprising at least 50 base pairs, having a sequence that is complementary to a second sequence of the target oligonucleotide and that has an initial nucleic acid polymerase binding site; b) denaturing DNA having the target sequence; c) hybridizing the upstream oligonucleotide primer and downstream oligonucleotide probe to the target oligonucleotide; d) binding a polymerase to the initial nucleic acid polymerase binding site; e) performing thermal cycling with a temperature range within 15°C of the Tm of the target nucleic acid sequence to extend the upstream oligonucleotide primer via polymerization with the polymerase toward the downstream oligonucleotide probe; f) cleaving nucleotides or small oligonucleotides of the downstream oligonucleotide probe;and g) detecting a signal resulting from said cleaving; wherein the downstream oligonucleotide probe is configured for a polymerase to cleave mononucleotides or small oligonucleotides at its 5' end, and wherein the Tm of the downstream oligonucleotide probe and the upstream oligonucleotide primer is within about 15°C of the target nucleic acid Tm.