Recently I found an alternative protocol to prepare cells to cell cycle analysis through flow cytometry using PI. In this protocol it is suggested to fix cells with 1% paraformaldehyde before fixation/permeabilization with 70% ethanol with the aim to avoid the aggregation of cells induced by ethanol. However I am questioning myself if the use of paraformaldehyde will avoid the exit of part of DNA from apoptotic cells allowing the observation of sub-G1 peaks. Please, somebody could help me?