By Levi Clancy for Student Reader on
TUNEL assay stands for terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling. When a cell undergoes apoptosis, it cleaves its genome. TUNEL assays use fluorescent dUTPs which bind to 3'-OH. The amount of cleavage is proportional to the amount of fluorescence. Therefore, apoptosis is represented by the degree of fluorescence.