stem cells from adults and is therefore not necessary to produce cells from embryos. But although research has shown that adult bone marrow cells can be transformed into liver cells, scientists believe that only embryonic stem cells could produce a complete range of tissue types. (Oliver 97)Cloning by nuclear transfer also has the potential for direct human applications-the production of embryos or even persons as a result of human cloning. These uses, however, are much more controversial, for they require the production of an embryo, fetus, or child with the same DNA as another. Such uses lie at the center of the current debate over the acceptability of human cloning and public policy toward it. . Cloning of embryos to treat infertility. - One likely use would be the cloning of embryos to enhance the fertility of couples, with viable egg and sperm going through in vitro fertilization (IVF) treatment for infertility. Cloning might occur by embryo splitting or by removing the cell or blastomeres of one or more embryos and placing them into enucleated eggs to create additional embryos. The purpose here either would be to assure the creation of enough embryos to start a pregnancy in cases when only one or two eggs are produced or to eliminate the high costs and physical burdens of additional hyperstimulated cycles and surgical retrieval. Cloning embryos in these ways would produce one or more embryos with the same genome (although mitochondrial DNA will differ, except in the case of embryo splitting). If they were placed in the uterus at the same time, they might produce two or more offspring with the same genome, resulting in the novelty of deliberately created twins. More problematic situations arise if a child is born from the first transfer, and the couple later thaws and transfers the other cloned embryos in order to have additional children. The result could be one or more children born at different points in time with the same geno...
