Ethical aspects of nuclear and mitochondrial DNA transfer.

Somatic cell nuclear transfer (SCNT) (cloning), as a reproductive or therapeutic method, and mitochondrial DNA transfer, as a method to prevent the transmission of mitochondrial diseases, are analyzed in this paper from a bioethics perspective. The licit purpose of being able to treat certain diseases, as in the case of SCNT, cannot justify, in any case, resorting to illicit means such as the manipulation, selection, and elimination of human embryos in the blastocyst phase, by using cell lines obtained from them. Crossing this line paves the way (as utilitarian ethics advocates) to assuming any cost in scientific experimentation so long as satisfactory results are obtained. With mitochondrial replacement, either human embryos are directly manipulated (pronuclear transfer) or germline cells are manipulated (maternal spindle transfer); changes in these could be transmitted to the offspring. LAY SUMMARY: This article analyzes somatic cell nuclear transfer (cloning) and mitochondrial DNA transfer techniques, in both reproductive and therapeutic applications, and preventive methods in the transmission of mitochondrial diseases, from a bioethical perspective. The manipulation, selection, and elimination of human embryos delimits the ethical acceptability of these promising techniques.