There are basically three ways to clone mammals. If it divides into an eight cell embryo and those eight cells are separated, those cells can be implanted into the uteri of eight separate mothers. Then eight clones will be born of different mothers. A technique known as twinning exists, but can only be used before an organism s cells differentiate. All cloning experiments of adult mammals have used a variation of nuclear transfer.
Nuclear transfer requires two cells, a donor cell and an oocyte, or egg cell.
Research has proven that the egg cell works best if it is unfertilized, because it is more likely to accept the donor nucleus as its own. The egg cell must be enucleated. This eliminates the majority of its genetic information. The donor cell is then forced into the Gap Zero, or G0 cell stage, a dormant phase, in different ways depending on the technique. This dormant phase causes the cell to shut down but not die.