DNA damage, percent tail DNA In a single cell gel electrophoresis assay (comet assay), percent tail DNA is the ratio of fluorescent intensity of the tail over the total fluorescent intensity of the head (nuclear core) and tail multiplied by 100. Originally from the CUAHSI HIS VariableNameCV. See: http://his.cuahsi.org/mastercvreg/edit_cv11.aspx?tbl=VariableNameCV. ODM2 Variable Name Controlled Vocabulary ODM2 Working Group A vocabulary for describing the name of Variables.