Method for detection of mutant gene

1. A method for detecting mutation(s) in a nucleotide sequence comprising:

performing a nucleic acid amplification reaction in the presence of DNA polymerase having exonuclease activity by using any one of the following oligonucleotides (a) to (d) or a salt thereof as a primer, using a probe labeled with a reporter fluorescent dye and a quencher dye, a dye labeled probe, or an intercalator, and using a nucleic acid in a sample as a template, and

detecting a reaction product in real time;

(a) an oligonucleotide,

i) wherein the oligonucleotide has the same nucleotide as a mutant nucleotide in a target gene at the 3′ end position thereof,

ii) wherein the oligonucleotide has the same nucleotide sequence as a nucleotide sequence of the target gene except for its 3′ end position, and has the same nucleotide sequence as the nucleotide sequence of the target gene toward the 5′-side from the position where the mutant nucleotide may exist in the target gene, and

iii) wherein the nucleotide at the second position from the 3′ end thereof has a modification that inhibits a reaction of nucleic acid synthesis,

or a salt thereof;

(b) an oligonucleotide,

i) wherein the oligonucleotide has a nucleotide complementary to a mutant nucleotide in a target gene at the 3′ end position thereof,

ii) wherein the oligonucleotide has a nucleotide sequence complementary to a nucleotide sequence of the target gene except for its 3′ end position, and has a nucleotide sequence complementary to the nucleotide sequence of the target gene toward the 3′-side from a position where the mutant nucleotide may exist in the target gene, and

iii) wherein the nucleotide at the second position from the 3′ end thereof has a modification that inhibits a reaction of nucleic acid synthesis,

or a salt thereof;

(c) an oligonucleotide,

i) wherein the oligonucleotide has the same nucleotide as a reference nucleotide in a target gene at the 3′ end position thereof,

ii) wherein the oligonucleotide has the same sequence as a nucleotide sequence of the target gene except for its 3′ end position, and has the same nucleotide sequence as the nucleotide sequence of the target gene toward the 5′-side from a position where the reference nucleotide exist in the target gene, and

iii) wherein the nucleotide at the second position from the 3′ end thereof has a modification that inhibits a reaction of nucleic acid synthesis,

or a salt thereof;

(d) an oligonucleotide,

i) wherein the oligonucleotide has a nucleotide complementary to a reference nucleotide in a target gene at the 3′ end position thereof,

ii) wherein the oligonucleotide has a nucleotide sequence complementary to a nucleotide sequence of the target gene except for its 3′ end position, and has a nucleotide sequence complementary to the nucleotide sequence of the target gene toward the 3′-side from a position where the reference nucleotide exist in the target gene, and

iii) wherein the nucleotide at the second position from the 3′ end thereof has a modification that inhibits a reaction of nucleic acid synthesis,

or a salt thereof,

wherein the nucleotide having a modification that inhibits the reaction of nucleic acid synthesis is represented by formula [I] or [II],

wherein B represents a nucleic acid base; R 1 represents an oxygen atom, a —NH group, or a lower alkylene group; and R 2 represents a lower alkylene group;

wherein B represents a nucleic acid base; and R 3 represents an oxygen atom, a nitrogen atom, a —NH group, or a lower alkylene group, and

wherein no reaction products are obtained if the 3′ end nucleotide of the oligonucleotide is cleaved as a result of the exonuclease activity of the DNA polymerase and the nucleotide having the modification which inhibits a reaction of nucleic acid synthesis at the second position from the 3′ end of the oligonucleotide becomes the 3′ end nucleotide of the oligonucleotide.

2. The method according to claim 1 , wherein the method further comprises an oligonucleotide as a primer capable of amplifying a sequence of interest by the nucleic acid amplification reaction in pairs with the oligonucleotide to be used as the primer in claim 1 .

3. The method according to claim 1 , wherein the primer comprises 15 to 30 bases.

4. The method according to claim 2 , wherein the combination of primers comprising “an oligonucleotide or a salt thereof having the same nucleotide as a mutant nucleotide in a target gene at the 3′ end position thereof; having the same nucleotide sequence as a nucleotide sequence of the target gene except for its 3′ end position, and having the same nucleotide sequence as the nucleotide sequence of the target gene toward the 5′-side from the position where the mutant nucleotide may exist in the target gene; and further having a modification that inhibits a reaction of nucleic acid synthesis at the nucleotide at the second position from 3′ end thereof”, and “an oligonucleotide capable of amplifying a sequence of interest by the nucleic acid amplification reaction in pairs with the oligonucleotide” is such a combination that when the nucleic acid amplification reaction is performed with the nucleic acid in the sample as a template, the objective reaction product is obtained if the nucleic acid in the sample is mutant type, and the objective reaction products is not obtained if the nucleic acid in the sample is wild type, and

wherein the detection is performed by detecting the mutant type of nucleic acid specifically by using the combination of primers.

5. The method according to claim 1 , wherein the mutation(s) in nucleotide sequence is a genetic polymorphism.

6. The method according to claim 5 , wherein the genetic polymorphism is due to a single base substitution, a single base deletion or a single base insertion.

7. The method according to claim 1 , wherein the nucleotide having a modification that inhibits the reaction of nucleic acid synthesis is a nucleotide modified with 2′-O,4′-C-Ethylene-bridged Nucleic Acids (ENA).

8. The method according to claim 1 , wherein the nucleic acid amplification reaction is polymerase chain reaction (PCR).

9. The method according to claim 5 , wherein the genetic polymorphism is due to substitution, deletion, or insertion.

10. The method according to claim 2 , wherein the primer comprises 15 to 30 bases.

11. The method according to claim 1 , wherein the detection of the reaction product is performed using an intercalator method.

12. The method according to claim 8 , further comprising the use of a probe labeled with a reporter fluorescent dye and a quencher dye.