zoobyshoe said:
I have no idea what this means, but it sounds interesting. Can you break it down a bit for someone who knows zilch about genes?
Oops...I thought that was the simple version. Gene expression is regulated by a lot of molecules within a cell, so when some external signal is received by an appropriate type of receptor on the cell, the receptor recruits in a variety of other molecules, and a cascade of molecular reactions and/or interactions occurs in the cytoplasm of the cell. Some of those molecules can get into the nucleus, and either directly act on chromosomes to change the rate of transcription (increase or decrease the expression of that gene) of some target genes. Which target genes are affected depends on special parts of the genetic sequence known as promoters, where the transcription factors "dock."
Here's an illustration that shows a little of each level, from extracellular to nuclear.
http://www.biocarta.com/pathfiles/h_p38mapkPathway.asp
There's a whole bunch of examples of various cell signalling pathways at that site:
http://www.biocarta.com/genes/CellSignaling.asp Some only show what happens in the cytoplasm, and don't really follow all the way through to the nucleus, but in some cases, you can put a few together to get the full picture. For example, this one gives a good idea of how complex the response can be:
http://www.biocarta.com/pathfiles/h_mapkPathway.asp
and if you note in that one all the way at the bottom right of the illustration, they show a molecule called NFkB (that's a kappa in there, but I don't know how to make one of those show up here). Then, on this other page,
http://www.biocarta.com/pathfiles/h_nfkbPathway.asp you can get more of an explanation of how NFkB gets to the nucleus to affect gene expression (the illustration doesn't match the description very well though...read the description part).
As you will get an idea very quickly, it's very complicated. People make careers out of studying just one pathway. But we definitely interact with our environment, so there must be ways for environmental signals to influence gene expression (note, I'm talking about gene expression...translating a gene to a protein...not the genome itself...that's what the original post talks about too, turning genes on or off...though it doesn't need to be all-or-none like that, it can be just increasing or decreasing expression).