The recent ruling by the FDA specifying that warning labels are not required on cloned beef has caused angst among some people who don’t understand the process or results of cloning. 

When a plant or animal cell reproduces, a process called “mitosis“, elaborate bio- and micro-chemical processes occur which (far more often than not) lead to the double-helix of the original DNA splitting into two identical halves.  These halves, as they are being ”unzipped” from the helix, are each copied perfectly by enzymes in the cell body.  The result is two flawless copies of the original DNA double helix molecule - each containing half of the original DNA molecule.  Other intracellular “machinery” then facilitates the splitting of remaining cellular components, including the “energy factory” mitochondrea organelles and eventually the “goop” (cytoplasm) in which cellular structures and molecules swim and the cell boundary itself.  When all components have been duplicated and/or split apart, the result is two identical cells. 

Shortly after splitting, each cell activates a specific subset of its genes (via signals derived from the physical and chemical “context” in which the cell finds itself) that direct each cell to acquire its own specific specialized chemical and physical properties.  This specialization is what allows a single nondifferentiated cell (often a stem cell) to become a specialist as blood, muscle, brain or other cellular component of an organism.

Cloning involves replacing the DNA of the first (or zygote) cell of an organism (and the organism’s first stem cell) with DNA extracted from another organism’s cell.  The newly-introduced DNA then takes advantage of the pliable structure and environment of the zygote to specify further development.  If all goes well, the organism develops to maturity based on the blueprint specified by the introduced DNA.  If all does not go well, the organism dies before developing completely.  In the case of successful development, the resulting organism is no less viable, no less biologically sound, and no less or more mysterious than any other organism of the same species.  Cloning does not introduce mutations, abberant properties, new emergent behaviors or structures, or foreign chemicals of any kind.  A cloned ear of corn, sheep, or cow is just as normal as any other corn, sheep or cow.  The only exceptional thing is that the DNA “recipe” for growing the organism is identical the recipie used for some other (donor) organism.

If the donor organism is particularly robust, disease-resistant, or produces a particularly significant yield of starch, protein, milk, silk or any other resultant substance, then the clone will be similarly and identically capable.  However, if this capability is to evidence itself, the environment in which the cloned organism matures must also be conducive to the development of the desired characteristic.  For example, plants must have sufficient water, soil nutrients and protection from pests.  Developing animals must have food, water, and environments free from physical and chemical stresses (assuming the results of such stresses are not themselves desired properties).

Creating clones is rather difficult, because of the physical and chemical trauma involved in extracting and inserting DNA from an into a cell nucleus; as such, many clone attempts fail.  As many as 90% of cloned organisms, do not live to be healthy adults because of cellular and genetic damage introduced during the cloning process.  Modern cloning techniques have increased the success rate and greatly reduced the damage done to the cloned cells, but the process is still complex and error-prone.

The context in which an organism develops has a significant bearing on the eventual emergent characteristics.  Studies with cat clones (and here) have shown that kittens grown from donor cells have radically different fur color-patterns.  These patters arise because pigmentation distribution is highly sensitive to the slightest change in conditions in which the organism develops in the womb of its mother.  An amazing new set of research into epigenetics has been yielding results showing that child organisms can inherit physiological properties of a parent through means other than DNA – once again, it’s all about the physical and chemical context provided by the mother and in which the organism develops.

Finally, the genetic instructions for building and running mitochondria, the energy-source structures for and inside cells, are contained with the mitochondria themselves, rather than in the cell’s DNA.  This material, encoded in RNA (a close cousin of DNA) is passed directly from the mother to her reproductive cell or egg, and is designated mRNA.  This mRNA is inherited completely independently of the DNA and completely unaffected by the father’s DNA contribution to a fertilized egg.  A cloned organism has its mRNA copied completely from the mother’s mRNA, “cloned” in fact.  This means the only organisms which are completely identical in terms of their genetic blueprint are identical (or maternal) twins, who share identical DNA *and* mRNA.  Maternal twins are more “clone-like” than are clones created by science.  But, we don’t put warning labels on identical twins nor accuse one of being less of a human than the other…

Putting aside the notion of human cloning (a whole other ball of twine), the notion that a cloned organism is somehow and uniquely dangerous is preposterous.  If a stock of crop or a breed of animal has proved itself highly fertile, disease-resistant, nutritious or otherwise robust, its clones will have these same identical properties because they come from the same genetic blueprint.  Disparaging the individuality of each organism is akin to saying a green 2004 Chevy Malibu has ambiguous moral and existential status because it is almost perfectly identical to a purple 2004 Chevy Malibu since, after all, they were made from identical blueprints with identically shaped parts.  Which Malibu is the “real” Malibu?  The one which came off the assembly line first?  Clearly, they are both perfectly good, substantial and viable cars, regardless of their relationship to one another.  The same holds for cloned organisms – each is a viable and valuable organism, regardless of how it came into being or what blueprints were used to construct it.  Further, neither the clone nor the donor is dangerous, inherently healthy or unhealthy, or infused with foreign and strange chemicals.  They are both living things, viable in their own right.

What about beef?  Given that cloned organisms (especially animals) still frequently display problematic growth, longevity and robustness, should we be concerned that eating cloned beef will somehow poison us?  The answer, surprisingly to some, is “no”.  The only way to get sick off of food is if the food contains viably reproducing microorganisms (e.g. viruses, bacteria, prions) which infect and infest the ingesting organism, or if there are poisonous chemicals present (e.g. mercury, dioxin).  Cloned beef may (or may not) be robust into old age, and there may be malfunctions in the way a cell behaves while it is part of a living creature, but such beef is not infested with harmful microbes or chemicals - it remains a great source of protein and fat.  Government studies have concluded that cloned beef is just as nutritious as non-cloned beef, and in no way whatsoever harmful.

People who want labels and warnings put on cloned products are likely more frightened by science fiction than science fact.  A label that says, “This is cloned” denotes an intellectual curiosity, but is not relevant to nutrition or health.  By intimating cloned food products are dangerous, when the science says otherwise, society would be reinforcing the tendency of people to make ill-informed decisions divorced from and contrary to fact.

Friday, December 29th, 2006 @ 2:00 pm Idle Thoughts, Science
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