NationStates Jolt Archive

Epigenetics has probably been around for a few years by now, but its interesting, and I am just now learning about. So in my Geology class, History of the Earth, we picked up on something today known as epigenetics. Basically what we learned is that through some research its been found that in some cases, acquired traits are passed on to offspring. I have a hand out here I am reading, and I will put it up here for everyone. After you are done reading it, or maybe researching it yourself, I want to know what changes this could bring about in medicine, science, and society, such as negative or positive outcomes. Its a very interesting subject, although I must say, I haven't made my mind up about it yet, as I haven't enough information on it.


This is my paraphrasing of the hand out:

Lamarck claims that Environment affects heredity. More or less Inheritance of acquired traits. For many years this was laughed at as being ridiculous since we know that Darwin's model is the correct way. Well perhaps Lamarck's theory was correct in a sense, albeit not in entirety.

So how exaclty does epigenetics work? Well, as we all know, DNA is an instruction set on how to build organisms. Its been observed in some organisms that in various enviroments, an organism genes might "switch on or off", with out changing the actual DNA. The genes have "switching memories" that passes on the information to subsequent generations.

Here are a few examples of what this is(straight off the sheet):

-Bacteria with DNA identical to their ancestors have immmune responses to an antibiotic if their ancestors were to that anti biotic.
-Bacteria subjected to various stresses tend to non-randomlydevelop the kinds of mutations they "need" for survival under those stresses
-Water Fleas (Genus Daphnia) develop defensive spines on the appendages when exposed to predators. DNA is the same but the presence of the predators turns on a genetic "switch" to build the spines. Genetic memony oof the need for spines is passed along to offspring.
- Agouti Mice carrying the Agouti gene begin to produce healthy, normal offspring if given a healthy diet. Furthermore, this gene being turned off has been passed onto further generations past the initial offspring.

a few resources:

Ghost in your Genes (http://video.google.com/videoplay?docid=-6992827937840416360&q=The+Ghost+in+your+Genes&hl=en)

Discovery Magazine, November 06 issue pages 33-37;75

Like I said, very interesting indeed. I'd like to see more info if anyone has it.

I'm not bought, for many reasons, which I'm going to address:

For your first example, I'm not terribly sure what you're getting at. Do you mean they show more of an immune response, or the same? It's worded rather oddly.

For the second example, depending on the stresses, it may appear non-random. The stresses applied may all but whipe out those without the genetics that would be favorable, allowing for those with it to thrive.

For your third example, this is a trait that in no way just forms. It is already encoded in their genetics for it to happen, and those with this type trait had a higher chance of survival, and thus breeding. This in no way proves Lemarck right.

For you last example, dealing with mice, it has nothing to do with evolutionary traits. The reason why they are healthier is not due to genetics, but diet. If you have a healthy diet, it allows the young to develop much better. You see, in the womb, where the fetus gets it's nourishment is from it's mother. If the mother is malnourished, that means that the fetus cannot develop as well, as there is not enough resources to develop well.

The main problem with LeMarck is that he is proven wrong time and time again. If you cut the tail off a dog, the young will always have a tail. Under Lemark, the young either would have a drastically shorter tail, or no tail at all, in basic terms.

Also, this is not taking into consideration that traits aquired during ones life almost never affect the genetic code, especially in the reproductive organs, which are mostly disconnected from the rest of the body. So really, there is a great deal of evidence against Lemarck's ideas, and aquired traits being passed on, in general.

Oye, I'm watching the vid now, and it's already a bunch of bull. For instance, they say there are 30,000 genes, and if one disease is caused by one gene, there simply aren't enough. Yet, they seem to forget there are nearly an infinite number of ways to construct these genes... leading to a nearly infinite number of possible combinations. I'm really not bought at all by this.

This is my paraphrasing of the hand out:

Lamarck claims that Environment affects heredity. More or less Inheritance of acquired traits. For many years this was laughed at as being ridiculous since we know that Darwin's model is the correct way. Well perhaps Lamarck's theory was correct in a sense, albeit not in entirety.

So how exaclty does epigenetics work? Well, as we all know, DNA is an instruction set on how to build organisms. Its been observed in some organisms that in various enviroments, an organism genes might "switch on or off", with out changing the actual DNA. The genes have "switching memories" that passes on the information to subsequent generations.

This isn't *entirely* correct. Epigenetic changes quite often are changes to the DNA - through methylation or demethylation of the various strands. The methylation/demethylation alters the coiling of the DNA strand, making certain genes more or less accessable.

The DNA code is not changed, but the DNA molecule itself is.

Some of these changes may be passed on to offspring, although there does seem to be some amount of reprogramming of epigenetic changes in the fertilization and development process. It is important to note that, unlike changes to the genetic code itself, these changes are reversible. Even if a given epigenetic change is passed on to offspring, differing environmental cues may change it back.

It's really interesting stuff though.

Epigenetics is pretty cool stuff.

It really makes a lot of sense when you think about it.

DNA does not exisit in a vaccuum. Genetic material is always passed on packaged in a cell. (well except in the case of virus' but not really clear that they are technically alive... another story).

So a creature's inheritence is not just the DNA itself, but the chemical context of the DNA is also passed on.

In higher organisms this is also exacebated by the fact that the environment of the early stages of development are entirely controlled by the mother.. ie conditions in the womb, pouch etc will effect the babies development.

There are some interesting studies being carried out with stress.. and mothers who were pregnant during 911 and thhe effect on their children.

While I don't think it is exactely Lamarckian in that chopping off your hand is not likely to mean that you kid is missing a hand... but the mother and the chemnical state of the egg will dramatically effect development .. and hence effect expression of certain traits.

ie its perfectly possible that you could have the gene for brown eyes but due to some chemical set up of the cells in your early development you end up with blue eyes (the default). You still have the gene for brown eyes .. but due to epigenetics you express a trait that is different to your genetics... (ignoring the fact that almost all babies are born with blue eyes.. I mean that they stay blue into later life).

Also, this is not taking into consideration that traits aquired during ones life almost never affect the genetic code, especially in the reproductive organs, which are mostly disconnected from the rest of the body. So really, there is a great deal of evidence against Lemarck's ideas, and aquired traits being passed on, in general.

The thing with epigenetic changes is that they are not changes to the code - that's the point. They are changes in how that code is used. Just as any given woman will usually have nearly an entire X-chromosome "turned off," the access of RNA polymerase/transcription factors/etc. to a given gene can be "turned on" or "turned off" by epigenetic changes as a result of environmental factors.

While it appears that many of those changes are reversed before getting passed on (take a look at the cloned cat and her lack of physical resemblance to the cat she was cloned from for an example of this), some very well may not be.

Epigenetics is pretty cool stuff.

It really makes a lot of sense when you think about it.

DNA does not exisit in a vaccuum. Genetic material is always passed on packaged in a cell. (well except in the case of virus' but not really clear that they are technically alive... another story).

So a creature's inheritence is not just the DNA itself, but the chemical context of the DNA is also passed on.

In higher organisms this is also exacebated by the fact that the environment of the early stages of development are entirely controlled by the mother.. ie conditions in the womb, pouch etc will effect the babies development.

There are some interesting studies being carried out with stress.. and mothers who were pregnant during 911 and thhe effect on their children.

While I don't think it is exactely Lamarckian in that chopping off your hand is not likely to mean that you kid is missing a hand... but the mother and the chemnical state of the egg will dramatically effect development .. and hence effect expression of certain traits.

ie its perfectly possible that you could have the gene for brown eyes but due to some chemical set up of the cells in your early development you end up with blue eyes (the default). You still have the gene for brown eyes .. but due to epigenetics you express a trait that is different to your genetics... (ignoring the fact that almost all babies are born with blue eyes.. I mean that they stay blue into later life).

Which in turn means that it is not necessarily traits which are inherited due to aquisition, but instead traits which are aquired due to development issues.

Really, aquisition of aquired traits is rather improbable(Unless the aquired trait is due to a mutation in an already existing strand, I suppose).

There is also work to do with trying to make offspring from 2 sets of male DNA (or 2 sets of female DNA) showing that there is essentially a battle going on between male and female DNA during development.

Fertilised eggs made with 2 sets of female DNA tend to just grow an enourmous placenta and no foetus ... and 2 sets of male DNA tend to grow the foetus much faster than the placenta and so the the foetus starves...

The genetic code would be valid.. but the chemical state of the DNA at the time of fertilisation effects the development process significantly enough to kill the foetus.

Which in turn means that it is not necessarily traits which are inherited due to aquisition, but instead traits which are aquired due to development issues.

Really, aquisition of aquired traits is rather improbable(Unless the aquired trait is due to a mutation in an already existing strand, I suppose).

I think you are missing the point.... there is a lot more to DNA than just the string of nucleotides...

I think you are missing the point.... there is a lot more to DNA than just the string of nucleotides...

Of course. I didn't mean to say otherwise. However, I am speaking against aquired traits being passed on, in the Lemarckian sense. Epigentics is interesting, but it's really not that remarkable.

Interesting. It reminds me of the Bene Gesserit in Dune...