Toehold-mediated DNA strand displacement provides unique advantages in the construction and manipulation of multidimensional DNA nanostructures as well as nucleic acid sequence analysis. We demonstrate a step change in the use of toehold-mediated DNA strand displacement reactions, where a double-stranded DNA duplex, containing a single-stranded toehold domain, enzymatically generated and then treated as a molecular target for analysis. The approach was successfully implemented for human DNA genotyping, such as gender identification where the amelogenin gene was used as a model target system, and detecting single nucleotide polymorphisms of human mitochondrial DNA. Kinetics of the strand displacement was monitored by the quenched Forster resonance energy transfer effect.