Binary probe and clamp compositions conduct methods for target hybridization detection. Where the probe is a substrate for exonuclease cleavage, the composition provides quantitation and detection of PCR products, by real-time and end-point measurements. Where the probe is an amplification primer, the composition provides an improved method for labelling and detection of PCR products. Probes and clamps may be labelled with fluorescent dyes, quenchers, hybridization-stabilizing moieties, chemiluminescent dyes, and affinity ligands. Clamps may be nucleic acid analogs, such as 2-aminoethylglycine PNA.