Embryos were collected for one hour and aged appropriately, then dechorionated and dounce homogenized. The homogenate was passed through Miracloth, further homogenized and nuclei were pelleted. Alternatively, Kc167 cells were cultured in Schneider's medium supplemented with 10% FBS. Cells were centrifuged, resuspended in 0.025% IGEPAL for 5.5 minutes and nuclei were pelleted.