By decreasing the HOMO energy gap between the base-pairs to increase the charge conductivity of DNA, the positive charge photochemically generated in DNA can be made to migrate along the pi-way of DNA over long distances to form a long-lived charge-separated state. By fine-tuning the kinetics of the charge-transfer reactions, we designed a functionalized DNA system in which absorbed photon energy is converted into chemical energy to form I-I covalent bonds, where more than 100 I-2 molecules were produced per functionalized DNA. Utilizing the fact that charge-transfer kinetics through DNA is sensitive to the presence of a single mismatch that causes the perturbation of the pi-stacks, single nucleotide polymorphisms (SNPs) in genomic sequences were detected by measuring the photon energy conversion efficiency in DNA by a conventional starch iodine method.