Patent ID: 7056671

Claim:
A method for amplifying a nucleic acid, the method comprising: (a) preparing a reaction mixture by mixing a nucleic acid as a template, a deoxyribonucleotide triphosphate, a DNA polymerase having a strand displacement activity, at least one chimeric oligonucleotide primer, at least one upstream block oligonucleotide and an RNase H, wherein the chimeric oligonucleotide primer is a chimeric oligonucleotide primer that is substantially complementary to the nucleotide sequence of the nucleic acid as the template and contains a ribonucleotide as well as at least one selected from the group consisting of a deoxyribonucleotide and a nucleotide analog, the ribonucleotide being positioned at the 3′ terminus or on the 3′-terminal side of the primer, and wherein the upstream block oligonucleotide is substantially complementary to a nucleotide sequence 3′ to a region in the nucleic acid as the template that is substantially complementary to the chimeric oligonucleotide primer, and the nucleotide at the 3′ terminus of the upstream block oligonucleotide is modified such that a reaction of complementary strand extension by the action of the DNA polymerase does not take place; and the upstream block oligonucleotide is capable of annealing to a region 3′ to a portion in the nucleic acid as the template to which the chimeric oligonucleotide primer anneals; (b) incubating the reaction mixture for a sufficient time to generate a reaction product; and under conditions in which specific annealing of the primer and the upstream block oligonucleotide to the nucleic acid as the template, an extended strand synthesis reaction and a strand displacement reaction by the DNA polymerase, and a reaction of cleaving the extended strand by the RNase takes place.