Stimulated by the success of animal cloning by nuclear transfer, some scientists have recently announced their intention to clone human beings by using the same technique. Basically, they would isolate nuclei from the cells of the donor wishing to be cloned, inject a diploid nucleus into an enucleated egg obtained from a volunteer female, and implant this egg into the womb of a surrogate mother. If all went well, the baby would be an almost exact genetic copy of the donor of the nucleus. We say "almost exact" rather than "exact" because human beings possess two types of genomes. The main genome resides in the cell nucleus and contains about 3.15 billion base pairs. However, human cells also contain mitochondrial DNA. Mitochondria are responsible for the production of energy and can be considered the energy factories of the cell. These bodies harbor a short piece of DNA that contains only about 16,600 base pairs. Thus, a human clone would still contain genes from mito-chondrial DNA originating from the mitochondria present in the enucleated donor egg.
In principle, there is no reason to believe that human cloning would not work, given that it does work in several other mammalian species. However, it is clear that human cloning raises major ethical questions, simply because human beings and human embryos are involved. First, there is the high risk of fetal malformation as seen in the cases of all presently cloned animal species. Do we have the right to produce individuals that may end up crippled because of the procedure that led to their creation? Then there is the potential psychological impact on a clone (and perhaps on the nuclear donor) of being the almost perfect genetic copy of one of his or her parents, while sharing little with the egg donor. Further, there are the horrendous complications regarding the kinship of a clone. For example, let us assume that the nuclear donor is a man. His cloned boy will be his son, but this son will have no mother, only a paternal grandmother in the female category. And how should the clone look at the woman who donated the enucleated egg? Would she be his mother? In a genetic sense, this "mother" would have only contributed mitochondrial DNA. Finally, since human cloning is reputedly sought mostly by infertile couples, the birth mother of the clone could very well be a surrogate, totally genetically unrelated to the "parents." In other words, the clone would have two "mothers" (the enucleated egg donor and the surrogate that brought him to term) and one father of whom he is a copy. Many other situations involving cloning can be imagined, and you are invited to do so.
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