We present a model describing the electrical conductivity and the current–voltage (IxV) characteristics along DNA finite segments within a tight-binding Hamiltonian model. To mimic the DNA molecule, we consider first a dangling backbone ladder (DBL)-DNA Poly(CG) sequences, whose building blocks are the bases cytosine and guanine. We found that the long-range (short-range) character of the correlations is important to the transmissivity spectra (IxV curves). Afterward, we investigate a Poly(CG-CT) DNA segment with diluted base pairing restricted to occur at a fraction p of the cytosine nucleotides, at which a guanine nucleotide is attached. We show that the effective disorder introduced by the diluted base pairing is much stronger in poly(CG) than in poly(CT) segments, with significant consequences for the electronic transport properties. Finally, methylated DNA strands sandwiched between two metallic electrodes are considered, whose IxV curves suggest potential applications in the development of novel biosensors for molecular diagnostics.