Indian Corn 2, by alicim, via Flickr (cc attribution license)
This post relates to non-Mendelian genetic changes that affect personality.
You may notice that this is the second post to associate Indian Corn with Keith Richards. The reason is that both have undergone epigenetic changes. One may argue that without these epigenetic changes, each would be uninteresting. Epigenetics does tend to mix things up – who’d want yellow corn or Keith Richards, insurance actuary?
Personality differences are as numerous as colors and patterns on Indian corn, and there may be a common genetic mechanism for the variation as well. Indian corn’s variety is due to “jumping genes” or transposable DNA elements that hop around the genome. . (Dr. Barbara McClintock got a Nobel Prize for figuring this out). (Note: *Sigh* re: the name “Indian”. To promote appreciation for our Native American crops, especially those as genetically interesting as this, below is a Native American recipe for blue corn muffins. )
What makes these little pieces of DNA hop around? In Indian corn, there are specific genetic signals (the AC/DS system, e.g., here), but as a general matter, no one cause has been found.
I think it is fascinating how non-Mendelian genetics -epigenetics – are turning out to be the key to personality.
Briefly, epigenetics is the study of changes in your genetic regulation due to environmental-ish factors. I say environmental-”ish” because there may be a genetic predisposition to epigenetic changes, or, your gene regulation may change after a life of hard chemically induced livin‘”
For the molecular biology wonks, generally, epigenetic changes are one of two types: those that silence genes (and prevent DNA->RNA->protein), and those that turn on genes to make, ultimately protein. Cytosine methylations at regions of gene promoters rich in CpG islands are generally associated with the silencing of genes, whereas histone acetylations are generally associated with the activation of genes. Apologies for the vast oversimplification, so here’s a PNAS article with a more full explanation, and describing elderly twin research, in which epigenetic drift changes one twin, but not the other.
(Strictly speaking, the transposable elements from Indian corn don’t fit in this definition, but the changes are extra chromosomal and, as readily observable, go straight to gene regulation. I also put trinucleotide repeat disorders in this category, perhaps for lack of a better category of non-Mendelian genetics.)
Here are Neurological Correlates’ earlier posts under the category “Epigenetics”, and some new information relating to epigenetic changes correlating with late on-set Alzheimer’s Disease
As a person ages, there can be an “epigenetic drift” into late onset Alzheimer’s. Here is a very enlightening discussion from an Alzheimer’s research forum. To again oversimplify, methylating the promoters (on-switches) for genes involved in Alzheimer’s plaques is variable, with those having late onset Alzheimer’s displaying particular propensities — regardless of the sequence of the underlying gene itself.
My guess is that a similar thing happens with personality disorders – epigenetic changes over time probably modify the course of the disorder. My own experience is that people who (again, in my own estimation) have some kind of dysfunction seem to get progressively worse with age. I’ve seen elderly narcissists become more severely paranoid and delusional (I’m not sure of the clinical psychiatric terminology, so big caveat, of course). This may be a dementia-overlay. As an additional question, is this because of self-medicating with drugs or alcohol? Is this kind of self-medication not only an immediate anesthetic for psychic pain but also a long term gene-regulation device?
We’ll find ways to stabilize our genes from epigenetic messing around. Here’s an interesting discussion at Neurophilosophy, where exercise is found to alter epigenetic predisposition (in mice, anyway).
But, on the other hand, this age-accumulation of epigenetic changes really adds to our personalities – even if, sometimes, the price is disease. So even if I could take a pill and make it so that my genes never change, would I want to?
That’s a roll of the dice. Would I like to stay the same, or take a chance on getting better or worse? I suppose if I decided to live out the rest of my life in true Keith Richards fashion, I’d probably be better off keeping epigenetic changes away from my genes as they are. On the other hand, if I took on massive amounts of exercise and healthy living, there’s certainly room for epigenetic improvement.
Here’s the recipe, from: “A River of Recipes,” Native American Recipes Using Commodity Foods, USDA Food Distribution Program on Indian Reservations, citing “http://www.cookingpost.com”
(Revision Date: July 2003)
Blue Corn Muffins
Makes 12 servings
1½ cups all-purpose flour
1 cup roasted blue cornmeal
3 teaspoons baking powder
½ teaspoon salt
1 teaspoon sweetener
½ cup instant nonfat dry milk + 1½ cups
water (or 1½ cups nonfat milk)
¼ cup egg mix + ½ cup water (or 2 eggs, well
1/3 cup vegetable oil
1. Preheat oven to 400ºF.
2. Sift flour, cornmeal, baking powder, sugar, and salt together.
3. Add milk, oil, and eggs. Mix until smooth.
4. Fill paper muffin cups ¾ full. Bake for 20 to 25 minutes.