Process using dual specificity oligonucleotide and dual specificity oligonucleotide

A primer set for selectively amplifying a target nucleic acid sequence comprising a pair of dual specificity oligonucleotides represented by the following general formula:

• 5′-Xp-Yq-Zr-3′ wherein,
• Xp represents a 5′-high Tm specificity portion having a hybridizing nucleotide sequence substantially complementary to a site on an initial target nucleic acid to hybridize therewith;
• Yq represents a separation portion consisting of contiguous universal bases;
• Zr represents a 3′-low Tm specificity portion having a hybridizing nucleotide sequence substantially complementary to a site on the initial target nucleic acid to hybridize therewith;
• wherein the initial target template nucleic acid is a nucleic acid molecule present in a sample to be analyzed prior to an amplification reaction using the pair of dual specificity oligonucleotides;
• p, q and r represent the number of nucleotides;
• p represents an integer of at least 15;
• q represents an integer of at least 5;
• r represents an integer of at least 3;
• X, Y, and Z are deoxyribonucleotides or ribonucleotides;
• the Tm of the 5′-high Tm specificity portion is higher than that of the 3′-low Tm specificity portion;
• the separation portion has the lowest Tm of the three portions;
• the 5′-high Tm specificity portion is longer than the 3′-low Tm specificity portion;
• the separation portion forms a non-base-pairing under conditions that the 5′-high Tm specificity portion and the 3′-low Tm specificity portion are annealed to the target nucleic acid, enabling the 5′-high Tm specificity portion to separate from the 3′-low Tm specificity portion in terms of annealing specificity to the target nucleic acid;
• whereby the annealing specificity of the dual specificity oligonucleotide is determined dually by the 5′-high Tm specificity portion and the 3′-low Tm specificity portion.