Cloning and embryonic stem cells: a new era in human biology and medicine

The cloning of mammals using adult cells as nuclear donors has been achieve d and the same procedure can be, at least theoretically, used to clone huma ns. Another recent technological advance, the derivation of human embryonic stem cells, opens up new possibilities in cell and tissue replacement ther apy and heralds significant improvements in gene therapy. Besides suggestin g new and potentially valuable medical applications, the insights gained th rough the use of these techniques could significantly enrich our understand ing of basic mechanisms regulating human development. On the other hand, th ese preliminary results are viewed by many as the opening of the Pandora's box and there are loud voices clamoring that research in these areas be for bidden in perpetuity. I suggest in the following article that at present we do not know enough to make anything but an entirely emotional decision abo ut future applications of these techniques. I try to summarize the current state of the knowledge in the field and indicate how much further research is necessary if benefits and drawbacks are to be properly understood.