Cloning of Animals and Humans: What Should the Policy Response Be?

CLONING OF ANIMALS AND HUMANS: WHAT SHOULD THE POLICY RESPONSE BEl PATRICIA A. BAIRD* I. Introduction The announcement by Wilmut, et al., in February 1997 that a lamb had been produced by transferring the nucleus of a cell from an adult sheep into an enucleated egg cell and implanting it took most people by surprise [I]. This largely unanticipated development demonstrates that asexual reproduction of mammals can be brought about, with the possibility it may also work in humans. This development has many implications that need to be thought through so that sensible and ethical policy can be put in place. This paper outlines the technology, explores possible applications and their social and ethical consequences, and suggests what reasonable and acceptable policy in this area might be. II. Definition and Description of Cloning The term cloning is used by scientists to describe different processes that make duplicates of biological material. Growing cells in culture so that cell lines are produced, or making multiple copies ofparticular DNA sequences by inserting them into bacteria and growing them, are both referred to as cloning. These uses of cloning do not produce individual organisms, but there are many uses of cloning in the production of plants and agricultural products where new organisms ere produced—for example, taking cuttings from one plant and propagating these genetic copies of it. However, it has not been possible to make copies of vertebrates in this asexual way until recent years. There are two cloning methods that can be used to produce The author would like to thank Morris Barer, Michael Burgess, Jan Friedman, Margaret Lock, and Fraser Mustard for helpful comments on this paper.»University of British Columbia, #222-6174 University Blvd., Vancouver, BC V6T 1Z3, Canada , e-mail: pbaird@unixg.ubc.ca.© 1999 by The University of Chicago. All rights reserved. 0031-5982/98/4202-1088$01.00 Perspectives in Biology and Medicine, 42, 2 ¦ Winter 1999 179 copies of higher organisms asexually: embryo splitting and nuclear transplantation (transfer) from somatic cells. The first method has been possible for some time and is used in animal husbandry for commercial purposes. It is usually termed "embryo splitting " but may also be called "blastomere separation." Within several cell divisions after fertilization of the egg, when the developing organism is still a small cluster of undifferentiated cells (blastomeres) , the cells making it up can be disaggregated. At this early stage, each cell is still capable of giving rise to a complete embryo (that is, it is totipotent) if it is implanted. Embryo splitting was used for the first time to produce additional human embryos in 1992, when investigators divided 17 chromosomally abnormal human embryos (which they therefore would not have implanted in a woman, and so which were not going to survive). From these embryos, they obtained a total of 48 developing embryos in vitro [2] . The second kind of cloning to produce an animal—the one that made headlines with the birth of Dolly—was done quite differently. A genetic copy of an adult animal was made, by-passing the usual reproductive process . An egg cell from one sheep was emptied of its nucleus and then fused with a somatic cell containing the nucleus of another adult sheep. This was then implanted in the uterus of yet another ewe. Dolly doesn't have two genetic parents, rather her genomic DNA is a copy of the DNA in the nucleus of an adult animal. In other words, she is a clone of that adult. Many researchers have tried in various species ofanimals to clone individuals from somatic cells, but have had little success. In amphibians, using a donor nucleus from an adult in an enucleated egg produced developing individuals, but these all died at the tadpole stage [3]. The key to Wilmut's success, where so many others had failed, seems to have been in using a method that made the donor nucleus and the cytoplasm of the recipient oocyte able to work together. He starved of nutrients those cells that would be used to provide the nucleus, to induce the nucleus into a quiescent phase of the cell cycle where many genes are shut down—the GO phase [1...