The invention relates to a method of synchronizing a population of somatic cells in G.sub.1 for purposes of preparing the cells for nuclear transfer or nuclear transplantation by using mechanical shake-off and selection of mitotic doublet cells. This method may further comprise cooling of the cells or other means of synchronizing the cells in G.sub.1 phase for longer periods of time. The invention also relates to the use of a synchronized population of rapidly, dividing somatic cells obtained by these methods as a source of donor nuclei or chromatin for use in nuclear transfer or nuclear transplantation.