This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
In-situ DNA nick end labeling can quantitate - 
Select and explain. 
A. Fraction of cells in apoptotic pathways, B. Fraction of cells in S phase, C. p53 gene produce, D. bcr/abl gene
A: Fraction of cells in apoptotic pathways
Answer: A: Fraction of cells in apoptotic pathways 
Explanation: 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 9/e p218