2.5 Analysis of DNA fragmentation by gel electrophoresis

Prior to gel electrophoresis, the DNA was ethanol precipitated with 0.1× volume of 3 M sodium acetate pH 5.2 and 2× volume of pre-chilled molecular grade ethanol, followed by centrifugation. Samples were centrifuged at 14000 rpm for 20 minutes, and the supernatant discarded. DNA pellets were air-dried and re-hydrated in 70 µL of DNA rehydration solution (Promega, Madison, WI). In order to separate DNA from cell debris, all samples were centrifuged at 6000 rpm for 5 minutes following the pellet re-hydration step and prior to gel electrophoresis analysis. To determine DNA fragmentation patterns, 40 µL of each sample was electrophoresed on 1.5% agarose gel in the presence of ethidium bromide.