Step 1: A somatic cell or body cell is taken from a donor.
Step 2: The DNA (46 chromosomes in humans) is removed from that cell.
Step 3: A female gamete (an egg or ovum) is harvested from a second donor and enucleated (its nucleus is removed). This removes the DNA (23 Chromosomes in humans) in the nucleus.
Step 4: The DNA from step 2 is inserted into the enucleated egg. At this point in human cloning, the egg would contain a full set of 46 chromosomes, all from a single donor. It would be the functional equivalent of a human zygote (the single cell organism created at conception by the fusion of sperm and ovum).
Step 5: The resulting cell is allowed to mature for a few days until it is a blastocyst (a pre-implantation embryo of about 128 cells).
Step 6: The following steps depend upon the purpose of cloning. There are two possibilities:
o Therapeutic cloning: ESC's are removed (embryonic stem cells) therefore destroying the blastocyst
o Reproductive cloning: the blastocyst is introduced into a woman's womb with the aim of initiating pregnancy.
Therapeutic cloning and reproductive cloning raise some very different ethical issues. Therefore they require that they be treated separately.
