Biology Reference
In-Depth Information
Transcription
Translation
[RNA]
Proteins
Degradation
Ribonucleotides
Fig. 14.4 The intracellular RNA levels denoted as [RNA] controlled by
transcription
and
transcript degradation
Generation
Elimination
[Phenotype]
Fig. 14.5 Evolution of novel phenotypes as a dynamic balance between
phenotype generation
and
phenotype elimination
(i.e., assumed the
transcriptional control stance
), so that whenever RNA levels
rose, it was interpreted as an indication that the corresponding transcription rate
increased. But the Garcia-Mainez et al. (2004) data clearly demonstrate that there is
no such one-to-one correlation between RNA levels and transcription rates as
evident in Fig.
12.6
, leading to the conclusion that the transcript-degradational
control must play an important role. The debate between
neo-Darwinains
and
anti-
Darwinians
may be analyzed in a similar way:
1. New phenotypes emerge as a result of the balance between two opposing
processes - “phenotype generation” and “phenotype elimination”:
2. Phenotypic variations can result from either
genotypic variations
(i.e., involving
DNA sequence changes) or
epigenetic mechanisms
(i.e., without involving any
DNA sequence changes).
3. Genotypic changes can be caused by
random mutations
,
recombinations
,
hori-
zontal gene transfers,
or
self-organized variational mechanisms
(as a part
of
active complexification processes
postulated to be inherent in the living
cell (see Sect.
14.2
).
Any successful theory of evolution that can replace neo-Darwinian mechanism of
evolution must take into account both
variation generation
and
elimination
as well as
all the complex mechanisms indicated in (2) and (3) above. Neo-Darwinians seem
to ignore the
generative process
. On the other hand, anti-Darwinians may be ignoring
the importance of
selection
(or
elimination
). If the scheme presented in Fig.
14.5
is
correct, both
variation generation
and
natural selection
(i.e., elimination) would be
important in evolution, just as the
transcription
and
transcript-degradation
steps are
equally important in determining RNA levels in cells (Ji et al. 2000a).
