What evolutionary advantage is there to the epigenome?

Why would there even be an epigenome? What's the point in creating genes, just to shut them down? And why pass these markers onto subsequent generations? Can anyone explain this?

 

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http://en.wikipedia.org/wiki/Epigenome#Functions_and_consequences

 

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Allows more rapid physiological response to environmental shift. Think about it as an additional adaptation at the level of the gene itself - the ecological "off switch".

 

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Say you have a gene "for" something - A causes 10 units of response in a good environment, 0 otherwise; a causes 5 units uniformly. Now say the environment suddenly prefers 0 units. All the AA genotypes are going to be able to survive, but not the aa genotypes or the Aa genotypes (since a is still producing 5 units; a funny kind of qualitative dominance).

 

But that does not explain why epigenetic markers are passed on to subsequent generations. How do the markers know what the environmental circumstances of a third generation offspring are going to be?

 

The success of that response must have led to proliferation of the genes that code for such a response.

 

But why would the response skip a generation?

 

They don't "know". But if the environment is prone to shifts, then the proliferation of such genes is likely - generation skipping might also match the sequence in environmental change. The ecological structure should also be investigated.

When you say "marker", I assume you mean an allele at a quantitative gene?

 

I don't know if it's an allele. I just saw a Nova special called, "Ghost in our Genes". It explained epigenomes, which I never knew about. It was a fascinating program, which displayed the power of markers to turn genes on and off. It also has disturbing implications, such as is it possible to create a chemical that produces markers that would make genes turn off and give you a dread disease. The possibilities for chemical warfare are frightening.

 

The success of that response must have led to proliferation of the genes that code for such a response. Either that, or it's an unintended consequence of some other response, perhaps an increase in the ability to survive a famine also has bad side effects.

 

Well, I suppose. But consider this: chemical warfare can just kill you anyway. No need to bother with DNA inactivation.

 

But is might be easier to produce and handle DNA inactivation chemicals.

 

Like pesticides? We are doing this to ourselves it seems.

 

I disagree. I think delivery and absorbance of regular nerve agents would be easier; it has a long history of experience and handling too. I can't believe that one would want DNA deactivation when a few micrograms of nerve agent would do the job. Who was it advancing the chemical warfare option?

 

But couldn't diseases caused by shutting off genes be potentially more psychologically frightening than nerve agents? "I'll screw you and all your progeny!"

 

I don't think so. I think just killing people would be easier. But: meh.

 

So we're all cool with epigenome?

 

This is an interesting conversation and my interest got piqued after watching the same Nova specia too. I went a completely different way with my thinking though. I came out of it with a completely different set of ideas about moving forward. To me it's possible that chemistry just isn't going to be the answer it seems like it will have to be some kind of a simulated social feedback and/or some kind of break though in radiation technology that will have an opposite effect of cancer causing radiation. Because you're talking about complex electrochemical signaling processes it doesn't seem very likely that chemistry will have the kinds of complex multiphase morphing solutions that will be effective for this. Even now chemists can't knowingly make side effect free meds because we don't understand completely what the chemicals that are being created do completely or how each body will respond various parts of the chemical compounds. It's unreasonable at this point or even maybe ever to expect that chemistry will change radically enough to morph and change to suit each person individually as their epigenome changes.

 

As for the whys...Atheists will say that the question "Why?" makes no sense since it's all random. Believer's on the other hand will say that when God said to treat your neighbors with dignity and respect etc. He/She did so based on the fact that He/She created us and knows a thing or four about how we respond to certain stimuli. It's not just about "Doing the Right Thing."

 

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