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2

Genotype, Phenotype, and Environment

the control of gene expression. The main challenge faced by an organism is a fluctu-

ating environment; the variety that the organism can bring to bear with its regulatory

networks must be at least as great as that of the variety of the environment in which

the organism seeks to survive (the principle of requisite variety ³). The regulation of a

single-celled microbe must be purely biochemical, but higher animals, starting with

the nematode worm C. elegans, have a nervous system and can respond in a more

sophisticated fashion. When the nervous system becomes as sophisticated as that

of man, the homeostatic response to, say, temperature fluctuations become enabled

by an apparatus of vast complexity, encompassing industries to extract and harness

fuels for heating and cooling, and to manufacture apparel, and vehicles for conveying

human beings to warmer or colder climes as desired.

The “environment” is often rather vaguely conceived as the surroundings from

which the organism is delineated as an autonomous entity within it. It is a source of

food, providing the energy needed to maintain order. But it is also a source, as well as

a sink, of information; the classical separation between microscales and macroscales

breaks down in nonconservative systems and there is a flow of information between

the scales. Random noise can thus be amplified up to macroscopic expression (Shaw

1981). It has been shown to be necessary for the formation of an ordered neural

network (Érdi and Barna 1984). This is the key to understanding why the information

content in the genes appears to be wholly inadequate to specify a three-dimensional

protein structure or neural connexions.

Problem. Estimate the amount of information needed to specify (a) the structure of a

protein, and (b) the neural connexions in the brain, and determine whether sufficient

information is available in the relevant repositories (i.e., the genome).

References

Ashby WR (1958) Requisite variety and its implications for the control of complex systems. Cyber-

netica 1:189–201

Bernal JD (1949) The physical basis of life. Proc Phys Soc A 62:537–558

Dupré J (2005) Are there genes? In: O’Hear A (ed) Royal institute of philosophy supplement, vol

56, pp 193–210

Érdi P, Barna Gy (1984) Self-organizing mechanism for the formation of ordered neural mappings.

Biol Cybern 51:93–101

Pirie NW (1937) The meaninglessness of the terms ‘Life’ and ‘Living’. In: Needham J, Green DR

(eds) Perspectives in biochemistry. Cambridge University Press, p 21

Polanyi M (1968) Life’s irreducible structure. Science 160:1308–1312

Polanyi M (2009) The tacit dimension. University of Chicago Press

Ramsden JJ (2001) Computational aspects of consciousness. Psyche Problems Perspect 1:93–100

Ramsden JJ (2010) Less is different. Nanotechnol Percept 6:57–60

Schrödinger E (1944) What is life? Cambridge University Press

Shaw R (1981) Strange attractors, chaotic behaviour, and information flow. Z Naturforsch 36a:80–

112

3 Ashby (1958).