Cloning, part four: Our genomes, ourselves

Let’s start with the worn chestnut of identity. Ethicist Robert Williamson has posited ‘that there is a personal right, ethically based, to individuality, autonomy, and identity…[and that r]eproductive cloning crosses a significant boundary in removing the single most important feature of autonomy: the fact that each of us is genetically unique.’ As is well reported, monozygotic siblings — so-called identical twins, triplets, &c. — seem to pose a challenge to the assertion to any such right, which convention would deem a universally inborn attribute (at least within our non-universal little branch of life’s tree). Williamson skirts this problem, distinguishing violations of rights by ‘nature’ from those ‘reproduced deliberately by man.’ Ignoring dilemmas raised in trying to justify or even rigorize such a distinction, he retreats still further, exempting monozygotic siblings as a special case because ‘even if they closely resemble each other, they do not resemble anyone else.’ Unfortunately for Williamson’s argument, the same can be said of clones and their clonees (except, say, if one of them happens to have a monozygotic twin, too…).

But even beyond the problems of defining rights, the identity question is moot. Simply put, clones are not genetically identical. To understand why, first recall an admonition that often pops up in the cloning debate: that environmental factors ensure the uniqueness of individual personality, aptitudes, and other large-scale (read: ‘non-genetic’) traits. If, for example, you rue the hackneyed vision of an army of Michael Jordan clones turning professional basketball into a Midas’s hell, check the numbers for a real life clone-of-a-sports-superstar. Outfielder Osvaldo Canseco hit exactly zero home runs in his major league baseball career; over the same seasons, his injury-prone monozygotic twin José hit 73, and swatted 389 more while Ozzie was relegated to the minor leagues or the celebrity impersonator circuit. Incidentally, José has reportedly written that both he and Ozzie used anabolic steroid supplements during their careers; while that particular environmental factor may have helped José considerably, it apparently did little for his twin.

Vagaries of environment turn out to affect more than athletic performance (which, of course, has genetic underpinnings too); they also affect the genome. Because genomes mutate, each potential clonee has a mildly genetically diverse population of cells from which to clone; further mutation during the development of a clone itself nearly assures its genetic uniqueness. Bottom line: assuming plausible rates of cell division and random mutation, fewer than one in ten billion newborn clones would have even one cell genetically identical to the sperm-fertilized egg from which he or she was derived.

Moreover, cloning — especially for males — may require eggs whose proteins (which influence gene expression, and, thus, subtleties of development) and non-nuclear genomes (such as those of mitochondria, the rife bacteria which long ago established symbiosis within ancestors of our cells) differ from those of the fertilized egg that became the clonee. A somatic genome transferred into such a tabula non rasa egg has its own pattern of functionally meaningful chemical modification (called genomic imprinting), too, which typically needs thorough overwriting for cloning. More bizarrely still, many living humans are technically chimeras, harboring small numbers of somatic cells derived from a mother, child, or even sibling; such cells sometimes cross placental barriers during gestation, engrafting amid much larger populations of cells derived from another zygote. In all the above cases, a clone derived from a single somatic cell represents a truly novel mix of heritable molecular inputs.

All told, the lack of strict genetic identity between clones and clonees voids any claim that cloning violates a right to genetic individuality. More importantly, it gives us more reason to treat clones as unique individuals, rather than to saddle them with overwrought expectations based on their genetic likeness to those we already know. Sadly, Brigitte Boisselier’s sect announced their own plans for the latter: to try to shoehorn — wholesale — the unique personalities and memories of clonees into the uselessly novel brains of their wards. Cloning’s own technical challenges pale next to those of such a cruel endeavor; and such doubly vain goals alarm those who fear cloning as a means to human eugenics.