Human cloning: ethical considerations

The 5 day old human embryo (blastocyst) is about 100 cells—roughly 30 inner cell mass (ICM) cells embedded in an outer layer. Removing these and culturing them leads to the production of pluripotent embryonic stem cells (ESCs) that can form any adult cell type. Current research involves removing ICM cells from blastocysts grown from the leftover fertilised eggs of in vitro fertilisation (IVF) treatment and their subsequent in vitro culture, with the donors' permission. Studying the development of ESCs into various adult tissues sheds light on early human development and may lead to novel therapeutic techniques.w1 Using ESCs from IVF, embryos diagnosed with a disease before implantation, such as Down's syndrome, permits the study of the progression of these diseases in culture and assessment of potential therapeutics.

Most countries permit generating ESCs for research, except the United States, which bans governmental grants for this research, other than for 72 established lines. Unfortunately, many of these are useless for research. The US government will soon have to redress the legislation or see mass migration of researchers.

Most of the current controversy comes from the ability to dictate the genetic identity of ESCs and producing them specifically for human cloning. Cloning involves the transfer of an adult somatic cell nucleus into a donor oocyte that has been stripped of its genome. After this enucleation, cleavage starts, and six days later the resulting blastocyst has the genotype of the adult somatic cell while showing a totally embryonic phenotype. Removal and culture of the ICM cells results in ESCs genetically typed to any adult …