MUST READ: Cloning the man on the Shroud of Turin
Cloning the man on the Shroud of Turin:
The Media’s Hyperbole with the Double Helix
The subject of a recent blog post about a comic book series that is now into its fifth issue, Punk Rock Jesus, involves a rather popular storyline regarding the Shroud: using DNA extracted from bloodstained threads to clone Jesus. Search on amazon.com and you will find over twenty fiction novels based on this premise; include those available exclusively as e-books and you can add about ten more. There has also been an Outer Limits television series episode, and a feature film released in 2010, “I’m not Jesus, Mommy”, centered on this idea.
Just how realistic is this scenario? What would be required to accomplish the cloning of a person under such circumstances? Would a clone be an exact duplicate of the Turin Shroud man? These and related issues are discussed below.
What exactly is cloning?
Cloning is the creation of an identical genetic copy of a living organism. Several types of cloning exist, but the most germane to the discussion of the Shroud is reproductive cloning using a method known as somatic cell nuclear transfer (SCNT). Somatic cells are cells other than sex cells (sperm or egg), which under normal circumstances do not provide DNA in the generation of an organism. Development of the SCNT technique began in the early 1950s using frogs, and was further refined and eventually popularized in the mainstream media years later with the success of Dolly, a cloned sheep, in 1996. The basics of this method are shown in the figure below. The nucleus of adult cell (a skin cell, for example) is isolated and transplanted into an egg cell (oocyte), which has had its own nucleus removed. The egg cell is then implanted into a surrogate mother, who also receives various hormones to simulate the normal course of pregnancy. Since the only source of nuclear DNA in the developing embryo is from the adult cell, the resulting offspring will be genetically identical to the organism from which it was taken.
In the creation of Dolly, the scientists used a very clever strategy to monitor their success: the skin cell containing the DNA to be transferred was taken from a type of sheep that was purely white-faced; the host egg cell into which this nucleus was transplanted was from a black-faced animal. If truly a clone, the offspring would have to be purely white-faced (which was also verified by DNA analysis). Cloning Dolly required significant effort; success was achieved only after 276 previous attempts by the same group resulted in failure.
Send in the clones
Since the creation of Dolly, other types of animals have been cloned using this method, including mice, rats, cats, dogs, goats, deer, cows, mules, and horses. To date, however, reproductive cloning has not been successful in primates. Although cloning of a Rhesus monkey was reported in 2007 (by embryo splitting), this is not equivalent to reproductive cloning by SCNT using DNA from adult cells in the creation of an exact genetic copy. Refinement of this method for use in primate cells has been especially hampered by the fact that removal of the nucleus from the egg cell disrupts important host proteins that are essential for subsequent division and development. It is certainly possible that current limitations to reproductive cloning in primates will be overcome in the future as techniques continue to be developed and refined. Reports of cloned human embryos have periodically surfaced in the media, but all have been subsequently found to be bogus.
Cloning and the Shroud
Apart from the existing technical roadblocks in the reproductive cloning of primates, if such a system were currently in place, cloning the man on the Shroud using DNA isolated from bloodstains still lies well within the realm of science fiction. Multiple problems exist with this scenario. First and foremost, to clone an organism, you need a full complement of nuclear DNA. The DNA on the Shroud is badly fragmented; while certain regions on particular chromosomes may be intact (for example, portions of the betaglobin and amelogenin X and Y genes sequenced by Garza-Valdes and coworkers), it is extremely unlikely that sufficient DNA is present to represent the entire genome. As mentioned above, even with technically pristine DNA present in a freshly isolated nucleus, successful transfer and development often requires numerous attempts together with a generous amount of luck.
Additionally, because numerous individuals are known to have handled the cloth, it is unclear that any DNA isolated would belong exclusively to the man on the Shroud. The average human being sheds approximately 400,000 skin cells per day, a portion of which contains DNA that may be transferred by contact, referred to as touch DNA; how long touch DNA may survive is unclear and unique to each object. The extent of contamination of the Shroud by exogenous DNA is unknown, but given the communal nature of the cloth in both its past and even more recent history, it is reasonable to speculate that DNA from numerous individuals may be present on the Shroud. If it were possible to obtain a full nuclear complement of DNA from a sample taken from the Shroud, it is likely to be a mosaic, resulting from the contribution of multiple persons. In the previously mentioned 2010 film “I’m not Jesus, Mommy”, the scientist responsible for the breakthrough, Dr. Gabriel, announces “What you are holding in your hands is the first human embryo cloned from red blood cells.” This is a miraculous feat indeed, as red blood cells in humans (and all mammals) are devoid of DNA because they lack a nucleus. In the non-Hollywood version, DNA from the Shroud would have to originate from white blood cells in the bloodstains.
A True Duplicate Copy: Ob-La-Di, Ob-La-Di or Ob-La-Da?
Ethical and moral issues aside, which are without question, hugely significant and relevant; and strictly speaking from a scientific viewpoint: if a full complement of intact, unfragmented nuclear DNA were available, and if it were purely from the bloodstains on the Shroud, and if current methods were in place for reproductive cloning in primates, would a clone be identical to the man on the Shroud? Genetically speaking, the answer is yes and no. Although a clone contains exactly the same nuclear DNA as the organism from which it originated, it is not entirely identical. There is no such thing as an exact clone. In addition to nuclear DNA, cells also contain mitochondrial DNA, which encode genes necessary for cellular function. In reproductive cloning, only the nuclear DNA is transferred to the donor egg cell. All mitochondrial DNA originates from the host egg cell, which will be expressed in the resulting organism (clone) throughout its lifetime. In normal organisms (non-clones), while nuclear DNA is inherited from both parents, mitochondrial DNA is transmitted solely from the mother.
Genes are only part of the story in the development of an organism. Environmental factors may influence which genes are turned on and which genes are switched off. Even monozygotic twins, which are truly genetically identical, do not have the same fingerprints. Twins that are raised together may appear at times indistinguishable, but each possesses unique personality traits and even physical features that are distinct characteristics. Unlike cinematic portrayals of cloning, which at times border on the irrational (e.g. Multiplicity, 1996), clones are not born as adults, equivalent in age to the individual from which they were propagated. A clone would be born as an infant and subject to unique experiences and environmental influences, which would impact the genetic blueprint. A clone would be expected, of course, to be very similar to the organism from which it came, but an identical carbon copy is not likely.
What the future holds in terms of cloning, particularly in relation to higher organisms, remains to be determined. Technology has advanced relatively rapidly compared to the full consideration of moral and ethical issues that accompany such scientific progress. Concerning the Shroud, such cloning scenarios are best categorized as science fiction rather than science fact.