Agro-Biotechnology: - The Greens | European Free Alliance

18 | Cloned farm animals - a ‚killing application‘? | Technical problems
reprogramming in the germ line cell:
“In sexually reproducing organisms, epigenetic variations have to survive the
complex process of meiosis in order to be transmitted to the next generation,
and, in multicellular organisms, they also have to survive gametogenesis
and early embryogenesis – two developmental stages that involve significant
restructuring of both cells and chromatin. (...) There is evidence that chromatin
marks and RNAs can be transmitted in this manner, but it is not clear how
this occurs. It seems likely that some footprints of chromatin marks remain
and lead to the reconstruction of ancestral states, or that some remnants of
ancestral states (including some RNAs) are retained.”
EFSA (2009) also acknowledges publications showing that RNA can be transmitted
via semen to the next generation, which is one of the possible transfer
mechanisms of epigenetic effects.
Furthermore EFSA (2009) mentions heteroplasmy in mitochondria as being
transferred to next generations. Here only a small number of animals was
investigated.
"It has been demonstrated that donor mitochondrial DNA (mtDNA) is transmitted
to clone offspring with varying efficiencies (Takeda et al., 2008). Four
cows (F1) with mtDNA heteroplasmy showed normal growth, productivity and
lactation characteristics and productivity.“
Given awareness that the mechanisms for epigenetic changes cause a high level
of unpredictability, a substantial health risk to following generations cannot
be ruled out. There is a certain likelihood that some of the adverse epigenetic
effects can escape restructuring during gametogenesis (becoming a cell in the
germ line of the cloned animal 19 ). The gametogenesis which is decisive for sexual
reproduction of the animals already starts during the growth of the embryo.
So far there seems to be some lack of understanding of whether the adverse
effects observed in embryos can also impact the genesis of the male or female
germ cells (FDA, 2008). It is surprising that the FDA (2008) nevertheless firmly
rules out any impacts on following generations.
It is quite plausible that effects in offspring generations of cloned farm animals
have hardly been observed so far due to the limited number of cases investigated.
Furthermore, some adverse effects might only appear under certain
environmental conditions such as stress or infectious diseases under conditions
of commercial farming. As Edwards et al. (2003) who were not assessed by
EFSA, explain, even seemingly healthy and normal clones might be affected by
deficiencies:
“However 'normal and healthy' cloned animals may appear, it is possible that
undiagnosed pathologies may develop later in life as a result of subtle changes
19 The cells in the germ line are those that ultimately become the sperm and egg.