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Mycoplasma capricolum, of the same family but with a genetic distance from the
M. mycoides, comparable to the distance between human and mouse genomes (this
bacterium was made DNA-free, by using a technique already available). The result-
ing artificial cell was named Mycoplasma mycoides JCVI-syn1.0. The new cell was
capable of self reproduction (a colony with blue color was obtained) and, as ex-
pected, it expressed the same proteins of the M. mycoides. In conclusion, the main
relevant facts were that: i) the genome of M. mycoides JCVI-syn1.0 was synthet-
ically assembled (with small changes), ii) M. mycoides JCVI-syn1.0 was a living
organism, iii) M. mycoides JCVI-syn1.0's life was driven by the replaced genome
which proved to be the real “operating system” of the cell. The crucial point of
the experiment was the M. mycoides JCVI-syn1.0's start-up. In fact, as we know
from computer operating systems, in order to make a system really operative for a
machine, a small set of instructions has to be executed which passes control to the
operating system, by activating its execution. This is a key point of the potency/act
passage, and it is not clear, as far as we know, what is the biomolecular basis of this
delicate passage. Of course, other steps need to be realized for a complete acquisi-
tion of the conceptual framework underlying this experiment of synthetic biology,
but in any case, this seems to be a great achievement toward a comprehension of life
by means of synthetic biology.
Cell genomes strongly resemble computer operating systems. Even in terms of
digital size, there is a remarkable similarity between the number of bytes of genomes
of complex organisms and the number of bytes of modern computer operating sys-
tems. If it is true that genomes establish how cells work, it is also true that the ways
they work are not completely determined by them. Therefore, the problem remains
of a better understanding of the relationship between these programs and their execu-
tion. In fact, the same genomes (genotypes) can produce different observable aspects
(phenotypes). Surely, the genetic determinism is not so strict as the analogous deter-
minism between computer programs and their executions. This suggests the research
of models which could disclose a more complex dialectics relating genotypes with
phenotypes. This is a key point for another aspect that is fundamental in life strategy:
the relationship between
programmability and evolvability
. The expressions of
genes (the programs executed in a given situation) result from a complex network of
interactions where external inputs play a crucial role. This means that, analogously
with complex computer programs, many conditions on control variables influence
the kinds of executions which can be performed. The simplest way of imagining
such a phenomenon is based on instructions which, at runtime, instantiate the value
of certain variables by values taken from external input channels, therefore, if condi-
tionalinstructionssuch as “ifX= ...then do...else ...” arepresentin theprogram,
then the contingent value of such control variables can dramatically change the ob-
servable program executions. Everything which influences the realization of genetic
programs, but is not directly related to genes, is defined as
epigenetics
.However,
this is only a negative definition, which does not say anything about the internal
mechanism which underlies the phenomenon of gene expression and regulation and
the way phenotypical patterns emerge from them [130, 153, 144, 119, 121, 132].
The model based on the external variable checkpoints is probably too simplified.
