Abstract: A rapid and sensitive detection method capable of reliably distinguishing fragments identical to a defined sequence from fragments containing a single base pair mismatch relative to the defined sequence. The method employs a peptide analog antisense probe, such as a peptide nucleic acid (PNA) probe, which hybridizes with DNA to forms complexes having higher thermal stability, but greater sensitivity to base pair mismatches, than corresponding DNA/DNA complexes. The method may be used in a number of applications, including genetic screening and hybridization sequencing applications.