The internucleosomal DNA ladder was only observed in apoptotic cells. A modification of the original method has made the detection of the DNA ladder much simpler. This modification involves the extraction of only the low-molecular weight fragmented DNA which is subsequently analyzed on a gel. 57 This drastically reduces the time required to analyze the cells, particularly when a large number of samples is to be tested. Another modification that increases the sensitivity of detection of the ladder is the utilization of the Southern blotting method following the gel electrophoresis step. 51 In such experiments, radioactively labeled sheared genomic DNA (same species as the DNA being tested) is used as the probe. This modification is very useful in situations where the amount of fragmented DNA is so low that detection in the gel by ethidium bromide staining is impossible.