Practice question

Among common sequencing platforms, Ion Torrent uniquely performs label-free, optics-free detection by sensing proton release during polymerization. When nucleotide is incorporated, hydrogen ion acidifies microwell, detected by ion-sensitive field-effect transistor, eliminating costly lasers, filters and fluorescently labeled nucleotides entirely. Sanger sequencing traditionally uses fluorescent dyed terminators or radioactivity, Illumina uses four-color reversible terminators requiring optical scanning, while pyrosequencing uses luciferase bioluminescence but still optical detection. Therefore Ion Torrent is correctly cited as method that completely avoids fluorescence dependence, substantially reducing instrument size and reagent cost.