 The probes will have a fluorophore linked to their 5’ end and a quencher molecule linked to their 3’ end.While the probe is intact, the quencher will remain in close proximity to the fluorophore, eliminating the fluorophore's signal.During the PCR amplification step, if the allele-specific probe is perfectly complementary to the SNP allele, it will bind to the target DNA strand and then get degraded by 5’-nuclease activity of the Taq polymerase as it extends the DNA from the PCR primers.