Detection of gene mutation through electronic transport properties measurements is an attractive research topic. For this purpose, we computed the current-voltage characteristics of adenine-thymine and guanine-cytosine nucleobase pairs, using a combination method of density-functional theory with non-equilibrium Green's function. Gene mutation was also simulated by structural change in nucleobase pairs by a double proton transfer mechanism. Four different metal electrodes were tested. Comparing the results, nucleobase pairs between platinum surfaces showed distinct electronic transport properties. Such as reverse rectifying direction and negative differential resistance behaviors. The discrepancy can be explained from series of electronic and structural analyses. All these results made identification of structural changes in individual DNA nucleobase pairs possible.