We present a now approach for the label-free characterization of genetic material. Time-resolved THz transmission analysis of polynucleotides demonstrate a strong dependence of the complex refractive index of DNA molecules on their hybridization state (hybridized/denatured). By monitoring THz signals one can thus infer the binding state of oligo- and polynucleotides, enabling the label-free determination the genetic composition of unknown DNA sequences. A broadband experimental proof-of-principle in a free-space configuration, as well as a first demonstration of a higher-sensitivity integrated approach using planar THz resonator sensors, are elucidated. The potential application for next generation high-throughput label-free genetic analytic systems is discussed.