Environmental effect on Phenotype

[Lukybear]

I was reading about the environmental effect on phenotype, and how there is a definite link. Firstly I am quite curious about the mechanism of this process; per say, does the environment trigger the genotype, which then triggers a phenotype? I.e. Can the environment switch of a gene? Or is it by some other mechanism that the environment affect the phenotype.

Secondld, if it does, (if it dosent, i am still quite interested to know) what is the molecular mechanism that turns a gene "off" assuming such a theory is scientifically valid.

[JackBean]

e.g. the enviroment may be limiting with some element and thus you won't be able to reach some phenotype

[jevg]

There is an inbuilt mechanism that determines the amount of variability in the phenotype.

You will find this paper very instructive, it’s conclusions are based on actual experimental data over some twenty years or so.
http://la.rsmjournals.com/cgi/content/abstract/24/1/71
You can down the full pdf
The summary is well worth absorbing. In part it states
“Utilizing methods established in twin research, only 20-30% of the range of the body weight in inbred mice were directly estimated to be of environmental origin. The remaining 70-80% were due to a third component creating biological random variability, in addition to the genetic and environmental influences. This third component is effective at or before fertilization and may originate from ooplasmic (the cytoplasm of an egg) differences. It is the most important component of the phenotypic random variability, fixing its range and dominating the genetic and the environmental component.” (my emphasis)

The scientific validity of the theory you have been reading about is not really being borne out from experimental data.
Genetic and environmental causes of variation are strictly limited in scope by other control and regulation machinery in the cell cytoplasm.

This understanding presents a possible reason why the LTEE experiment has produced such a minor result in evolutionary terms. I have posted the information of this experiment in this thread
about18763-12.html