A method of detection and discrimination of target DNA sequences and of single nucleotide polymorphisms (SNPs) directly on double-stranded DNA (dsDNA) samples without the need for denaturation of the target dsDNAs. This is achieved by the use of a PNA chain as a probe. This probe is self-assembled on a gold electrode; hybridization of the probe with the target dsDNA forms a PNA-dsDNA hybrid. The hybrid is then labeled with a mediator, and the PNA-dsDNA hybridization is monitored. Monitoring of the hybrid formation can be achieved using an electrochemical approach. This method is able to detect and discriminate target DNA sequences and SNPs on ds-oligonucleotides. Furthermore, this method is able to detect and discriminate target DNA sequences and SNPs on double-stranded PCR products.