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September 2, 2011 | Posted By David Lemberg, M.S., D.C.

The first human clone has not yet been born, but the fields of molecular biology and reproductive genetics are making rapid progress. Methods for cloning mammals have been available for more than a decade. Attempts to clone a primate utilizing these technologies have not yet been made, and it’s likely that human cloning will present even greater challenges. But the overall structure is in place.

In mammalian cloning, an adult skin cell is reprogrammed to a primitive pluripotent state. Primitive, in this context, refers to a very early stage in the history of the cell’s development, rather than a prehistoric or backward condition. Pluripotent cells have the capability to develop into any type of cell lineage, such as muscle, blood, gastrointestinal, or nerve cells. The adult cell is in a differentiated state — it possesses highly specific structure and has highly specific tasks, based on its cell type. Reprogramming an adult cell to pluripotency dedifferentiates the cell, and makes it possible to use that cell’s DNA as source material to fertilize an egg whose DNA has been removed. This process of dedifferentiation, injection of DNA, and fertilization is termed somatic cell nuclear transfer (SCNT).

Of course, SCNT involves technology. The technology is brilliant and may work to the extent that a living, thriving clone is created. But the technology is used to replace physiological processes that have been perfected over hundreds of thousands of years. Technological substitutes may distort or interfere with critical events or may introduce new elements which will ultimately be destructive to the clone and/or its descendants.

The above argument is similar to those used to oppose introducing genetically modified organisms into the environment. On these views, fooling with Mother Nature is probably a very bad idea. With respect to human cloning, the danger involves causing permanent alterations of unknown consequence to the human genome.

For example, the process of dedifferentiation (restoring pluripotency) involves genes and regulatory proteins that are also involved in cancer formation. Pluripotent cells are effectively unregulated cells — one of their primary characteristics is the ability to self-renew. Cancer cells are similarly unregulated — they are notoriously self-renewing. It is possible that in the process of causing an adult cell to dedifferentiate, various cancer-causing genetic programs are configured and set to stealth mode. Such programs will result in cancer development upon activation by complexes of environmental signals.

If such a conjecture is accurate, SCNT and human cloning would lead to increases in cancer susceptibility, permanently enshrined in the genomes of the clone’s descendants. With respect to non-human clones such as the storied (and deceased) Dolly the Sheep, these alterations have not been demonstrated. But creating a clone via SCNT may sidestep other genomic safeguards, resulting in novel permanent alterations to the human genetic code. If sufficient alterations accumulate over numerous generations, the evolving human genome may no longer accurately be called human.

The Alden March Bioethics Institute offers graduate online masters in bioethics programs. For more information on the AMBI master of bioethics online program, please visit the AMBI site.

0 comments | Topics: Bioethics and Public Policy, Genetics, Health Care Policy, Stem Cell Research


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BIOETHICS TODAY is the blog of the Alden March Bioethics Institute, presenting topical and timely commentary on issues, trends, and breaking news in the broad arena of bioethics. BIOETHICS TODAY presents interviews, opinion pieces, and ongoing articles on health care policy, end-of-life decision making, emerging issues in genetics and genomics, procreative liberty and reproductive health, ethics in clinical trials, medicine and the media, distributive justice and health care delivery in developing nations, and the intersection of environmental conservation and bioethics.
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