Classical apoptotic cell death can be defined by certain morphological and biochemical characteristics that distinguish it from other forms of cell death. One such feature, which is a hallmark of apoptosis, is DNA fragmentation. In dying cells, DNA is cleaved by an endonuclease that fragments the chromatin into nucleosomal units, which are multiples of about 180-bp oligomers and appear as a DNA ladder when run on an agarose gel. Here, we present commonly used methods such as conventional agarose gel electrophoresis to analyze fragmented nuclei in cells. The various methods used are dependent on the extent of fragmentation or the amount of fragmented nuclei in a sample. Determining whether a cell exhibits DNA fragmentation can provide information about the type of cell death occurring and the pathways activated in the dying cell.
