- INTRODUCTIONCell cycle studies in Drosophila embryos have led to increased understanding of how cell proliferation is regulated during development. It is not yet possible to synchronize Drosophila embryos with respect to their cell cycle phase. Thus, cell cycle stage-specific extracts cannot be prepared and analyzed. An alternate approach is to analyze individual Drosophila embryos during syncytial divisions. This protocol describes a procedure for rapidly fixing precellular-stage embryos and selecting those of the desired division cycle stage for further analysis.