Wednesday, July 23, 2008

The New Larmarckism

One of the most remarkable developments in biology in years is the discovery of epigenetics. A more technical discussion is down below, but let me start with an analogy.

DNA has often been described using a recipe metaphor. The recipe is just some words on a piece of paper, but describes how to combine ingredients in the environment to produce a dish.

A chocolate cake is quite different in looks and taste to the ingredients that go into it. And we all know that the quality of the ingredients, as well as the skill of the cook combining them, can dramatically influence how that cake turns out. Even though the recipe is exactly the same.

It's the expression of the recipe that makes the difference between good cake and OHMYGODITSDELICIOUS! cake.

This last idea is Epigenetics. That is isn't just our DNA (recipe) that determines how we will develop. How that DNA is read and expressed has just as much to do with the outcome as the basic recipe does.

Which means that what you eat, drink, smoke, huff, shoot, and accidentally expose yourself to can affect not just your body for that hour, day, or week, but how your cells will develop from then on. And more importantly, it can affect how your kids will develop as well, long after the exposure.

(For you Intelligent Design advocates out there, if you think the recipe analogy makes the case for an Intelligent Chef being necessary for the meal, I'm afraid you are once again confusing scintillating metaphor for scientific method. They are not the same. One is a useful method for predicting outcomes, the other is just words that tell a story. Sound familiar?)

More Technically...

[Wikipedia] ...the term epigenetics refers to changes in gene expression that are stable between cell divisions, and sometimes between generations, but do not involve changes in the underlying DNA sequence of the organism.[1] The idea is that environmental factors can cause an organism's genes to behave (or "express themselves") differently, even though the genes themselves don't change.
This is huge.

Your environment (which includes what you eat and breathe, as well as what you *do*, like exercise, read, think) can cause a change in gene expression. This concept has been around a couple decades, and is being exploited in all kinds of genetic therapy ideas (viral, miRNA, siRNA).

What's new and interesting is that these changes can be permanent. They can stick around through cell replication, so all new cells of that type now behave differently in the same way. This is epigenetics.

And what's truly new and remarkable is that it has been shown that these permanent markers that change gene expression can also modify germ cells (sperm, and probably eggs) in the same way. Meaning that what happens to you in your environment can not only change you, it can change the genetic legacy you pass on to your children!

Early indications are that many forms of cancer, schizophrenia (and other mental health failures), obesity may be caused not only from your environment, but could have been caused by experiences of your parents or grandparents.[link - requires subscription]

For example, if Mom smoked before getting pregnant, but quit and never smoked again once she had you, your genetic expression will still be different than if she had never smoked at all.

This is just the teeny, weeny beginning of a whole new understanding of how evolution and genetic expression works. Soon we will not only be able to cure our own genetic disorders, we can make these fixes permanent and inheritable. A further understanding will allow actual improvements to your existing genetic recipe. And these can be passed along to the next generation as well.

Have you ever thought, "If I could change anything about myself, what would it be?"

Start making your wish list.

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