<prompt> In-situ DNA nick end labeling can quantitate -Fraction of cells in apoptotic pathwaysFraction of cells in S phasep53 gene producebcrabl gene  <response>: In Situ Nick-End Labeling An in situ method for detecting areas of DNA which are nicked during APOPTOSIS. Terminal deoxynucleotidyl transferase is used to add labeled dUTP, in a template-independent manner, to the 3 prime OH ends of either single- or double-stranded DNA. The terminal deoxynucleotidyl transferase nick end labeling, or TUNEL, assay labels apoptosis on a single-cell level, making it more sensitive than agarose gel electrophoresis for analysis of DNA FRAGMENTATION. Ref Robbins 9e p218 