Patent ID: 7494790

Claim:
A method of synthesizing a nucleic acid molecule comprising: A) mixing the following components 1) to 3) with sample nucleic acid as a template: 1) a primer set consisting of four distinct oligonucleotide primers, wherein: the first oligonucleotide primer comprises (i) a 3′ terminal nucleotide sequence that anneals to a sample single-stranded nucleic acid molecule and serves as the origin of synthesis for synthesizing a first single-stranded nucleic acid molecule complementary at least in part to the sample single-stranded nucleic acid molecule and (ii) a 5′ terminal nucleotide sequence that is complementary to an arbitrary region of the first single-stranded nucleic acid molecule; the second oligonucleotide primer comprises (i) 3′ terminal nucleotide sequence that anneals to the first single-stranded nucleic acid molecule prepared using the first oligonucleotide primer and serves as the origin of synthesis for synthesizing a second single-stranded nucleic acid molecule complementary at least in part to the first single-stranded nucleic acid molecule, and (ii) a 5′ terminal nucleotide sequence that is complementary to an arbitrary region of the second single-stranded nucleic acid molecule; the third oligonucleotide primer comprises a nucleotide sequence which anneals to a region of the sample single-stranded nucleic acid molecule, wherein said region is located 3′ to a region where the first oligonucleotide primer anneals and outside of a region defined by the outer nucleotides of the first oligonucleotide primer; and the fourth oligonucleotide primer comprises a nucleotide sequence which anneals to a region of the first single-stranded nucleic acid molecule, wherein said region is located 3′ to a region where the second oligonucleotide primer anneals and outside of a region defined by the outer nucleotides of the second oligonucleotide primer; 2) a DNA polymerase having strand displacement activity; and 3) one or more nucleotides which are used by the DNA polymerase to extend the primers; B) incubating the mixture at such a temperature that the nucleotide sequence constituting the first and third oligonucleotide primers can form stable base pairing with the template; and C) synthesizing a nucleic acid having complementary sequences linked alternately in a single-stranded chain; wherein the first oligonucleotide primer and/or second oligonucleotide primer anneals to a loop capable of base pairing which is formed by hybridization of the complementary sequences.