Provided herein are methods and kits for discriminating a target sequence from a reference sequence in a polymerase chain reaction (PCR), comprising a labeled probe comprising a fluorophore and a quencher that is complementarity to and specifically binds to the target sequence and may non-specifically bind to the reference sequence and a promiscuity-blocking nucleotide juror oligonucleotide (PBNJ) that specifically binds to the reference sequence and may non-specifically bind to the target sequence, wherein the PBNJ comprises a reference binding region and an extension blocker that prevents elongation by a polymerase.