Patent ID: 8206929

Claim:
A method of selective amplification of a desired variant of a target sequence, which target sequence exists in the form of more than one variant, the method comprising the steps of: a) providing a sample possibly comprising at least one variant of the target sequence in a reaction mixture; b) providing a first oligonucleotide, capable of hybridizing to more than one variant of the target sequence; c) providing a second oligonucleotide, capable of hybridizing to more than one variant of the target sequence, wherein at least a fraction of said second oligonucleotide contains a modified base in one or more nucleotides at or near the 3′-terminus; d) providing a third oligonucleotide, capable of hybridizing to the desired variant of the target sequence with lesser affinity than to an undesired variant of the target sequence and designed to hybridize to the same strand and between 0 and 60 nucleotides downstream of said second oligonucleotide; e) providing a nucleic acid polymerase substantially lacking 5′-3′ nuclease activity; f) subjecting said reaction mixture to polymerase chain reaction, wherein said third oligonucleotide substantially inhibits extension of said second oligonucleotide by said nucleic acid polymerase when said third oligonucleotide is hybridized to the undesired variant of the target sequence, but does not substantially inhibit extension of said second oligonucleotide by said nucleic acid polymerase when said third oligonucleotide is hybridized to the desired variant of the target sequence.