Nuclear transfer from somatic cells provides a wide range of opportunities, both in basic and applied research. However, the efficiency of the nuclear transfer procedure remains low. The fundamental reasons are that the basic mechanisms of nuclear transfer are unclear. The research work in the past on these questions have shown that two groups of factors have multiple effects on the reconstructed embryos in nuclear transfer. The first are those involved in maintaining ploidy of the reconstructed embryos and the second are in reprogramming the donor nuclei. Some of the cell cycle interactions between the donor nucleus and recipient cytoplasm are reviewed.