Science a GoGo's Home Page Forums General Discussion General Science Discussion Forum epigenetics for Samwik

Just saw a TV program that seems to cover aspects Samwik was getting at regarding non-genetic inheritance. I googled the scientist mainly quoted (Marcus Pembrey) and found these. Hope they help you, Sam:

http://discovermagazine.com/2006/nov/cover/article_view?b_start:int=3&-C=

A paper from the man himself:

http://www.nature.com/ejhg/journal/v14/n2/full/5201538a.html

And from good old Wiki:

http://en.wikipedia.org/wiki/Epigenetics

Cool Terry!
Thanks! So far I've only seen this:

Meaney says, "We're beginning to draw cause-and-effect arrows between social and economic macrovariables down to the level of the child's brain. That connection is potentially quite powerful."
"Epigenetics will have a dramatic impact on how we understand history, sociology, and political science," says Szyf. "If environment has a role to play in changing your genome, then we've bridged the gap between social processes and biological processes. That will change the way we look at everything."

...and
http://discovermagazine.com/2003/nov/you-are-what-your-mother-ate/

"If the mother is nutritionally deprived or oversupplemented at those times, the expression of some genes in the child will be permanently altered."

Thanks again; more later....
~Samwik

From your link:

"The methyl molecules have the greatest impact during periods of rapid cell division, such as when an embryo is only a few cells old."

I remember from the TV program (it's probably in one of my links as well) that the critical period was at the time of gamete formation. For males this is at puberty and for females when their own eggs are forming while they are still a developing embryo. So probably in most cases the impact is a bit further along in development than when "an embryo is only a few cells old."

All goes to show evolution is not a simple process.

Terry,
Not at all simple, as you say.

I think some people have been using some of these new findings to dispute evolution theory (it "shows" Darwin was wrong).
Read up to be prepared!

Anyway, I finished those links (not all of wiki, but...).
Regarding your post above:

Discover wrote:
"The methyl molecules have the greatest impact during periods of rapid cell division, such as when an embryo is only a few cells old." ["such as" other times too...and lesser "impact" at slower times too]

Terry, I ran across this above in the Discover article, but it wasn't referring to the same "critical period" that the other article was referring to:
"the major exposure sensitive period detected in the paternal grandmother was when she was a fetus/infant. With respect to the paternal grandmother's SGP, it is perhaps relevant that recent evidence from mice show that oogenesis continues after birth."
For other parameters that they looked at, it was ages 7 & 9 where epigenetic effects were noted to "originate."

...some dramatic statements:

"The clear pattern of specific, limited 'exposure-sensitive' periods throughout the paternal grandparents' development from conception to adulthood (Figure 1a), including a switch in the direction of the transgenerational association during the SGP (slow-growth period), confirms the importance of the SGP and suggests the existence of an evolved transgenerational response mechanism."

"In rats paternal dexamethasone exposure in utero led to both a reduced birth weight and increased hepatic activity of the gluconeogenic enzyme, phosphoenolpyruvate carboxykinase, in future offspring.[19] Beyond studies of mutagenic agents,[20] we are not aware of any general male-line transgenerational studies in humans. This probably stems from two factors; residual scepticism[21] about the germline's susceptibility to environmentally-induced change and epigenetic inheritance (with its hint of Lamarkism), and the fact that human transgenerational studies are fraught with problems."

"However, the coherence ... supports the hypothesis that there is a general mechanism for transmitting information about the ancestral environment down the male line."

...and other stuff for the female line.

"Our findings add a new, multigenerational dimension to the interplay between inheritance and environment in health and development; they provide proof of principle that sex-specific, male-line transgenerational effects exist in humans. We propose that our results, which are specific enough to allow replication, are manifestations of an evolved adaptive transgenerational response mechanism. Our study exemplifies a research approach that could, potentially, make a major contribution to public health and impact on the way we view our responsibilities towards future generations."

...and many of the titles, in the list of References at the end of the article, look like a magical journey themselves!

~Samwik

Thanks Sam. Got to go pretty soon so I'll read it tomorrow.

Samwik wrote:

"some people have been using some of these new findings to dispute evolution theory (it "shows" Darwin was wrong)."

Even in my first link it says:

"Such results hint at a seemingly anti-Darwinian aspect of heredity."

Perhaps. But as Wiki says:

"the observation of epigenetic change occurring in response to environmental factors opens up the possibility of adaptive inheritance — a sort of Lamarckian inheritance. Although this remains speculative, if this does occur some instances of evolution would indeed be separate from standard genetic inheritance."

Neither Darwin nor Lamark knew anything about how characteristics are inherited so any new discoveries in that field affect their theory not one bit. In fact, of course, epigenetics offers further support for evolution. But I notice that even "Discover" seems to be hoping to increase circulation by claiming evolution may be wrong.

By the way, thanks for the bit:

"recent evidence from mice show that oogenesis continues after birth."

I didn't know that. I thought the number of eggs a female was born with, that was it.

I've been meaning to point out that this idea does suggest Lamark was not totally on the wrong track. If the environment leads to some advantageous epigenetic effect perhaps a subsequent genetic mutation would stabilise it in the population. We tend to think mutations are random but perhaps hormones or other signals in the body provide some impetus. Apparent Intelligent Design. So God is within us. Wow. Better go to the not quite science forum.

Yes! One of the reasons I think epigenetics is important to know about is that I can see the ID'ers using some quotes [w/o context?] to support either points that "transcend" normal genetics, or to support points that "prove" normal genetics (or classical evolution) as wrong or False!
...based on the way ID'ers have "used" science so far.

It helps to be armed with some perspective, just in case.

~SA

Thanks for the warning, Samwik. You wrote:

"I can see the ID'ers using some quotes [w/o context?]".

That's normal. I've read the quote by Henry Gee many times in creationist literature, "All the evidence for human evolution ... can be fitted into a small box". The dots replace, "between about ten and five million years ago". Changes the sense quite markedly doesn't it.

Of course Darwin got it wrong. Gradual change leading to progress was how his social class viewed their own progress resulting from the industrial revolution. If the uprisings of 1848 had been successful we would have known about punctuated equilibrium a hundred and fifty years ago.