Deoxyribonucleic acid (DNA) bio-polymers derived from fish waste products are employed as gate dielectric in n-type methanofullerene as well as p-type pentacene based organic field-effect transistors working at low voltage levels and low gate leakage currents. Based on the large hysteresis in the transfer characteristics, operation of the transistor as a non-volatile memory element is shown. Practically hysteresis free operation of DNA based transistors is obtained at low voltage levels by adding an additional aluminium oxide blocking layer between the organic semiconductor and the DNA gate dielectric.