Biology Reference
In-Depth Information
noise is a reduction in the information carried by the protein rel-
ative to what it would have been if the transmission were perfect,
i.e. if the protein strictly corresponded to the DNA. If, however,
instead of considering the transmission of the information from its
source to its arrival, one were now to envisage the total quantity
of information in the entire system, of which this transmission
pathway is but a part, one can quite easily show that the quantity
of information produced by the noise is added and not subtracted.
That can be understood intuitively: errors end in a protein, the
structure of which is not an identical reproduction of that of the
DNA, and they therefore introduce new variability which represents
diversity, compared with what would happen if there were no
errors. This diversity can obviously be the source of poor function-
ing and produce negative effects, but in certain cases, it may on the
other hand be the source of an increase in complexity, and possibly
of functional complexity — with an overall positive effect for the
system
”
29
(FTG pp. 25-27).
In order to translate this theory into a concrete biological
mechanism, which is capable of explaining how cells function, Atlan
stressed the sources of redundancy in organisms. He particularly
emphasised the existence of DNA sequences which are repeated
countless times in the genome of multicellular organisms, his idea
underlying this being that their mutation during embryonic devel-
opment could play a functional role, as is the case with the syn-
thesis of antibodies in the immune system, (CF pp. 70-72; FTG
p. 28). In addition, there are bound to be random variations in the
concentrations of biological molecules inside cellular compartments,
caused by thermal agitation. Atlan also suggested that these varia-
tions may be a source of self-organising noise.
However, as he himself emphasised, whether the noise comes
from the environment or has to do with fluctuations in chemistry
or diffusion, it is always a disturbance to normal functioning of the
system and as such, is an external factor (CF pp. 56-57, 81-82).
29
Translated from the French by Margaret Hutchings.
