The Cellar - Epigenetics

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- - Epigenetics (http://cellar.org/showthread.php?t=21911)

I've been reading up on the latest advances in epigenetics for awhile now, because there is research implicating the concept in everyone's favorite dead-horse childhood disease. But it has implications for a huge number of diseases, including cancer, diabetes, Alzheimer's, and even aging itself. There's a very accessible article in Time this month on it:

Quote:

We have had a long-standing deal with biology: whatever choices we make during our lives might ruin our short-term memory or make us fat or hasten death, but they won't change our genes — our actual DNA. Which meant that when we had kids of our own, the genetic slate would be wiped clean.

What's more, any such effects of nurture (environment) on a species' nature (genes) were not supposed to happen so quickly. Charles Darwin, whose On the Origin of Species celebrated its 150th anniversary in November, taught us that evolutionary changes take place over many generations and through millions of years of natural selection. But Bygren and other scientists have now amassed historical evidence suggesting that powerful environmental conditions (near death from starvation, for instance) can somehow leave an imprint on the genetic material in eggs and sperm. These genetic imprints can short-circuit evolution and pass along new traits in a single generation.

Quote:

For instance, fruit flies exposed to a drug called geldanamycin show unusual outgrowths on their eyes that can last through at least 13 generations of offspring even though no change in DNA has occurred (and generations 2 through 13 were not directly exposed to the drug).

if no change in DNA has occurred, how could the trait be passed? They must mean no 'detectable' change to the DNA.

perhaps this is an indication that we don't know what we think we know about the genome of the subject?

Any change to the sperm or egg will be passed to the child. DNA is the strongest and most versatile agent of such change, but not the only one.

Everything else. Everything in a zygote cell is from the sperm or the egg, and it all self-replicates. DNA creates the protein building blocks, but there is all sorts of cellular machinery that uses them to make more cells. Any of it could be affected by a drug or other stimulus. Most of those [disruptive to cell reproduction] effects would probably kill the cell, and most of the rest would probably resume normal operation in the absence of the stimulus, but some could permanently change the operation.

I have a vague memory of a somewhat recent story about prions (or something similar) that did this. Prions can change the output of DNA without affecting the DNA, by changing the way proteins fold.

Quote:

Originally Posted by lumberjim (Post 628292)

if no change in DNA has occurred, how could the trait be passed? They must mean no 'detectable' change to the DNA.

<sigh>
Read the article.

Quote:

At its most basic, epigenetics is the study of changes in gene activity that do not involve alterations to the genetic code but still get passed down to at least one successive generation. These patterns of gene expression are governed by the cellular material — the epigenome — that sits on top of the genome, just outside it (hence the prefix epi-, which means above). It is these epigenetic "marks" that tell your genes to switch on or off, to speak loudly or whisper. It is through epigenetic marks that environmental factors like diet, stress and prenatal nutrition can make an imprint on genes that is passed from one generation to the next. >>

YEAH...i never click links....sorry, i know that frustrates you.

this was the bit that i was wondering about.