DNA molecules possess unique structure and molecular recognition properties that makes them excellent candidate for bio-chemical sensors. Understanding the mechanism of charge transport in DNA is essential to develop DNA based molecular electronic devices. In the experiment reported in this thesis, we analyzed an electrical method to detect specific DNA. Hairpin probe DNA was engineered to melt and hybridize with certain perfect complementary sequences and immobilized on a silicon chip between gold nanoelectrodes. Hybridization of target DNA to the hairpin melts or open up the stem nucleotides, which provides DNA hybridization sites. Gold nanoparticle-conjugated universal reporter sequence detects the open sites of hairpins by annealing to the exposed stem nucleotides. The gold nanoparticles along with the DNA facilitate the movement of electrons, hence increasing the charge conduction between the electrodes. Specifically, we used a hairpin probe designed to detect a medically relevant mutant form of the K-Ras oncogene. Direct I-V measurements of the nanoelectrodes both before and after the DNA attachment showed three orders of magnitude increase in conductivity for as low as 2 fmol of target molecules.