Epigenetics of Reproduction in Animals - Building the Most Complex Structure on Earth - page 67

Even if, for the sake of argument, one ignored all of the above difficulties and
took for granted that the genome can do all of the above, another insuperable dif-
ficulty looms: which of the genomes will function as directing center of the develop-
ing organ?
1. All the genomes of the myriad cells of the organism;
2. Genomes of cells participating in the development of the organ; or
3. The genome of a particular cell that sends instructions for the development to all the cells
of the presumed organ.
If 1 is true, the embryo would hardly avoid a “developmental chaos.”
If 2 is true, the genome of these cells has to be (initially at least) different from
the genomes of the rest of the cells of the embryo, which is irreconcilable with the
basic tenet of molecular genetics that the genome in all somatic cells of the body is
identical.
If 3 is true, this would be a master genome, which is refuted by 2.
Let us again suppose that the above difficulty is also surmountable. Then another
insurmountable difficulty pops up from the nature of individual development: during
the intrauterine life, many mammal species, including humans, form quadrillions of
specific neural connections. Obviously, not only tens of thousands of genes, but also
the entirety of the few billion nucleotides in the genome of these species, are negligi-
ble as a source of information for determining the huge number of neural connections.
Given that there is no evidence that a gene, a number of genes, or the genome
does determine the sequential signals or chemical instructions leading to the devel-
opment of the phenotype, one cannot reasonably believe that the development of
an organism, from a single cell (zygote or egg) to the complex structure of an adult
metazoan organism, results from the implementation of any genetic program.
From a genecentric view, it is incomprehensible how from an initial developmen-
tal program different programs emerge that are operational in tens to hundreds of
different types of cells in a metazoan organism. The cell differentiation that leads to
these modified programs is determined and regulated epigenetically ( Juliandi et al.,
2010; Maruyama et al., 2011 ) rather than genetically: “Cellular differentiation is a
well-orchestrated epigenetic program by which the developmental potential of the
cells is progressively restricted” ( Maruyama et al., 2011 ).
Epigenetic Information
In 1942, English scientist Conrad H. Waddington invented the term epigenetics to
describe the interaction of genes with their environment and the phenotypic result
of this interaction, as opposed to a one-to-one correspondence between the geno-
type and phenotype. Before and after that, only scant evidence existed on inherited
nongenetic changes in phenotypic traits. So, for example, the German zoologist
Richard Woltereck (1877-1944) observed that under cultivation, the Danish strain
of the small crustacean Daphnia cucullata produced offspring with helmets, and
this Dauermodifikation (long-lasting modification) lasted for up to 40 genera-
tions before reverting to the ancestral type. He attributed these inherited changes to