
Scientists discover 'hidden' code in DNA evolves more rapidly than genetic code - J3L2404
http://www.sciencedaily.com/releases/2011/09/110916152401.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily+%28ScienceDaily%3A+Latest+Science+News%29
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zeteo
It's an interesting study, but the article is somewhat lacking. First off, the
title is imprecise. This is specifically about epigenetics (DNA methylation).
"Hidden code in DNA" is very vague, and can also apply, for instance, to
introns, which are also fast evolving.

Second, it is questionable to what extent the term "evolution" can apply to
DNA methylation, since these changes are usually lost within a few
generations.

Third, epigenetics are relatively inconsequential for animals, for which the
Weismann barrier is hardly ever penetrated:
<http://en.wikipedia.org/wiki/Weismann_barrier>

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bmahmood
Agree that this article isn't the most descriptive, and evolutionary may not
be the best of terms, but it should be noted that epigenetics has caught the
eye of developmental and neurobiologists for some time as explaining much more
of human traits/behavior than our DNA itself.

The human genome is composed of roughly 20K protein-coding genes, not enough
at all to code for all the complexities in our body (if there was a gene for
every bifurcation in our capillaries, we'd run out of genes pretty fast; in
addition to the fact that there is no single gene for specific human
behaviors, i.e. "aggression").

Epigenetics, in its simplest form as DNA methylation, provides a powerful
solution to many of the issues of "there aren't enough genes", and explains a
lot of the chaos-elements / environmental impacts on heritability of traits.

DNA methylation, by consequence of wrapping the DNA in chromatin, controls
access to which genes get turned off/on by transcription factors (TF). TFs in
turn are often influenced by environment, especially neonatal. If you do the
permutations of which genes are on/off, b/c a TF can/can't access the DNA, b/c
the chromatin is on/off = a whole new set of permutations that entail a new
information code.

A good example of the impact of epigenetics is obesity. Children's propensity
to obesity often has a lot due to with epigenetic influences during neonatal
development. For instance, if a mother is pregnant during a famine and thus
doesn't eat much, the fetus' digestive system will adapt to starving
conditions through epigenetic changes in chromatin that bind the relevant
genes, thus developing a "thrifty metabolism" (digests food slowly). This
trait then stays through generations, and when such people move to the West,
their metabolisms incline them towards obesity as their body still digests
food slowly thinking they were born into starving conditions.

So long story shot, epigenetics aren't "evolutionary" in the original sense,
but they are redefining how traits/behaviors (too complex to be explained by
genes) are inherited/developed.

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rue
> _A good example of the impact of epigenetics is obesity. Children's
> propensity to obesity often has a lot due to with epigenetic influences
> during neonatal development. For instance, if a mother is pregnant during a
> famine and thus doesn't eat much, the fetus' digestive system will adapt to
> starving conditions through epigenetic changes in chromatin that bind the
> relevant genes, thus developing a "thrifty metabolism" (digests food
> slowly). This trait then stays through generations, and when such people
> move to the West, their metabolisms incline them towards obesity as their
> body still digests food slowly thinking they were born into starving
> conditions._

I think it'd be fair to characterise this as an early hypothesis?

~~~
bmahmood
The exact mechanism is still being studied for sure, but the phenomenon is
well documented and continually researched (article a couple years back:
<http://www.pnas.org/content/105/44/17046.short>).

The most widely cited example in humans is "Dutch Hunger Winter"

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tlammens
No wonder that there are people who believe in "intelligent design" with
headlines like that. The word 'hidden' could be interpreted as someone or
something has hidden it there.

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gojomo
Maybe Lamarckism wasn't all wrong!

