above the method of the present invention provides a simple and sensitive means for assessing the identity and the amount of a target dna in a sample the following examples are given for the purpose of illustration only and are not intended to limit the scope of the invention an au electrode with an area of 2 mm 2 mf 2014 aue gold electrode bas in usa was sequentially washed with hot 2 m naoh for 5 min and then with concentrated nitric acid for 5 min followed by two cycles of ultrasonic treatment in distilled water each for 3 min the electrode was dipped in an aqueous 0 1 m sulfuric acid solution and the voltage applied thereto was cycled between 0 to 1 5 v at a rate of 100 mv s using a voltammetric analyzer bas cv 50w in usa until the current originating from contaminants was no longer detectable to determine a basal line the bare electrode thus obtained was treated with a 1 mm 2 mercaptoethanol 2 me solution for 2 hr to induce sulfide bond formation between the u2014 sh group of 2 mercaptoethanol and the electrode surface the resulting electrode was coated with a monolayer of covalently bonded u2014 s u2014 ch 2 ch 2 u2014 oh the terminal u2014 oh group being extended outwards using an oligonucleotide synthesizer sense and anti sense oligonucleotides of sequence numbers 1 and 2 were prepared and then a phosphoric acid group was joined to the 5 u2032 end of the sense oligonucleotide 1 ethyl 3 3 dimethylaminopropyl carbodiimide hydro chloride edac and the sense oligonucleotide ssdna were dissolved to concentrations of 1 u03bcg u03bcl and 1 mm respectively in a 40 mm 2 n morpholino ethanesulfonic acid mes.