用常规琼脂糖凝胶电泳ＵＶＢ照射后培养不同时间的ＮＩＨ３Ｔ３细胞ＤＮＡ，两个样本均未出现凋亡梯形带，而用相同条件处理的昆明小鼠胸腺细胞ＤＮＡ出现了典型的梯形带．再用反转电场琼脂糖凝胶电泳（ＦＩＧＥ）ＵＶＢ照射后培养不同时间的ＮＩＨ３Ｔ３细胞ＤＮＡ，发现ＤＮＡ先断裂成低于２３ｋｂ的大分子片段，然后进一步断裂成小分子片段，但始终未出现梯形带，说明ＤＮＡ并不总是从核小体之间断裂的． The DNA of NIH3T3 cells cultured at different times after UVB irradiation by conventional agarose gel electrophoresis showed no apoptotic trapezoidal band in both samples, while DNA of thymocytes in Kunming mice treated with the same conditions showed a typical trapezoidal band. The DNA of NIH3T3 cells cultured at different times after reverse electric field agarose gel electrophoresis (FIGE) was irradiated. It was found that the DNA was cleaved into large fragment below 23kb and further broken into small molecule fragments, but no trapezoid Bands indicate that DNA is not always broken from nucleosomes.