Analysis of DNA content and DNA strand breaks for detection of apoptotic cells

This unit describes a method for identifying apoptotic cells based on in situ detection of DNA strand breaks. Correlated analysis of DNA content and DNA strand breaks allows one not only to identify apoptotic cells but also to pinpoint their location in the cell cycle. The basic protocol uses 5-bromodeoxyuridine triphosphate to label the 3-OH termini of the breaks, but the procedure is easily adapted to a variety of other conjugates. Given the multiplicity of commercially available reagents it is possible to label DNA strand breaks with a dye of any fluorescence color and excitation wavelength.