Dolly, “Only 2-5% of cloned animal embryos grow into health offspring” (Anon, 2007: 802). There are definitely quantitative differences that are important. The problem of hydroallantois rarely occurs in natural cattle pregnancies but occurs at a rate some twenty times higher for pregnancies established with cloned embryos compared to IVF embryos (40% and 2%, respectively).(Wilmut et al., 2002) The rate of stillbirths in a study of heifer cloned cattle by Infigen was 24%; this rate is 3.5 times the rate in Canadian Holstein heifers (6.9%) (Lohuis et al., 1993, available at http://cgil.uoguelph.ca/pub/articles/stillbirth.html). A study of the frequency and occurrence of late-gestation losses from cattle cloned embryos found that the overall rate of live births from IVF embryos was more than 7 times the rate for adult somatic clones (49% vs 6.8%, respectively) (Table 1 in Heyman et al. 2002). The incidence of loss for late-gestation losses (between Day 90 of gestation and calving) was 43.7% for adult somatic clones compared to 0% in the control IVF group. Also, a review article on SCNT, found that the number of clone embryos that developed to become live young was between 0 and 4%, a figure far lower than that for other assisted reproduction technologies (Wilmut et al., 2002). In sum, quantitative differences are important.
Secondly, and more importantly, there are unique risks associated with SCNT. In the Risk Assessment, FDA claimed that the only real risk associated with SCNT is the problem of epigenetic reprogramming associated with putting the nucleus of a differentiated somatic cell into an enucleated egg (egg which has had its nucleus artificially removed); the genes in the nucleus of that somatic cell must be reprogrammed so that they can act like they come from an undifferentiated cell. This is in fact a unique risk, and contradicts FDA’s claim that there are no unique risks. As the FDA argues, “incomplete or inappropriate epigenetic reprogramming appears to be one of the primary underlying causes for the relatively low success rate of cloning, and the source of potential subtle hazards for the consumption of food from animal clones.” The FDA then focuses its discussion of epigenetic reprogramming on the methylation of DNA as the major component influencing epigenetic regulation of gene regulation.
However, there are two areas that the FDA ignores that represent unique risks posed by SCNTs: the effect of nuclear-mitochondrial interaction arising from a donor nucleus and epigenetic restructuring of somatic chromatin, e.g. aberrant histone acetylation. The issue of nuclear-mitochondrial interactions is an important one as the FDA has focused almost exclusively on epigenetic reprogramming problems as being a major cause of SCNT failure and has ignored the issue of mitochondrial dysfunction. Mitochondria are called the powerhouses of the cells as they are the main suppliers of energy, in the form of ATP, for cellular functions. In addition, mitochondria play critical roles in cell signaling and programmed cell death (Hiendleder et al., 2005).
Finally, mitochondria have a small genome that is separate from the nuclear genome (Lloyd et al., 2006). Mitochondrial DNA (mtDNA) codes for some of the proteins involved the electron transport chain (ETC) pathway. The mtDNA also codes for a number of transfer RNAs and ribosomal RNAs. However, all the proteins involved