A method for detecting or quantitating a first allelic variant of a target sequence in a nucleic acid sample suspected of having at least a second allelic variant of the target sequence, said method comprising: (a) forming a reaction mixture by combining: (i) the nucleic acid sample; (ii) an allele-specific primer, wherein an allele-specific nucleotide portion of the allele-specific primer is complementary to the first allelic variant of the target sequence, and wherein the allele-specific primer comprises at least one nucleic acid modification; (iii) an allele-specific blocker probe that is complementary to a region of the target sequence comprising the second allelic variant, wherein the allele-specific blocker probe comprises a non-extendable, 3'-hexanediol, blocker moiety and at least one nucleic acid modification; (iv) a detector probe; and (v) a locus-specific primer that is complementary to a region of the target sequence, wherein the region of the target sequence complementary to the locus-specific primer is: 3' from the first allelic variant; and on the opposite strand; and (b) carrying out an amplification reaction on the reaction mixture using the locus-specific primer and the allele-specific primer to form an amplicon; and (c) detecting the amplicon by detecting a change in a detectable property of the detector probe, thereby detecting the first allelic variant of the target gene in the nucleic acid sample. (a) forming a reaction mixture by combining: (i) the nucleic acid sample; (ii) an allele-specific primer, wherein an allele-specific nucleotide portion of the allele-specific primer is complementary to the first allelic variant of the target sequence, and wherein the allele-specific primer comprises at least one nucleic acid modification; (iii) an allele-specific blocker probe that is complementary to a region of the target sequence comprising the second allelic variant, wherein the allele-specific blocker probe comprises a non-extendable, 3'-hexanediol, blocker moiety and at least one nucleic acid modification; (iv) a detector probe; and (v) a locus-specific primer that is complementary to a region of the target sequence, wherein the region of the target sequence complementary to the locus-specific primer is: 3' from the first allelic variant; and on the opposite strand; and (i) the nucleic acid sample; (ii) an allele-specific primer, wherein an allele-specific nucleotide portion of the allele-specific primer is complementary to the first allelic variant of the target sequence, and wherein the allele-specific primer comprises at least one nucleic acid modification; (iii) an allele-specific blocker probe that is complementary to a region of the target sequence comprising the second allelic variant, wherein the allele-specific blocker probe comprises a non-extendable, 3'-hexanediol, blocker moiety and at least one nucleic acid modification; (iv) a detector probe; and (v) a locus-specific primer that is complementary to a region of the target sequence, wherein the region of the target sequence complementary to the locus-specific primer is: 3' from the first allelic variant; and on the opposite strand; and 3' from the first allelic variant; and on the opposite strand; and (b) carrying out an amplification reaction on the reaction mixture using the locus-specific primer and the allele-specific primer to form an amplicon; and (c) detecting the amplicon by detecting a change in a detectable property of the detector probe, thereby detecting the first allelic variant of the target gene in the nucleic acid sample.