Recent progress of animal cloning

I was reported that adult somatic cells could be reprogrammed in enucleated oocytes and developed to a normal sheep after nuclear transfer in 1997. But, it is also clarified that the successful rate of animal cloning is still very limited. One of the possible reasons for the low success is the failure of reprogramming of somatic cells in ooplasm after nuclear transfer. Failure of the reprogramming of somatic cell nuclei in ooplasm causes variedabnormalities to SCNT embryos in every developmental stage, including both preimplantation and postimplantation stages, and resulted in the low successful rate at birth. But the mechanism of reprogramming or reprogramming factors in the enucleated oocytes are still unclear.I will review the recent progress of animal cloning in this talk. Especially, whether goodembryos can be selected before embryo transfer, and how to raise the viability of clonedembryos after implantation will be discussed.