Just when I’m beginning to understand genetics (in the most superficial sense) along comes epigenetics. I’ve got it down that genes are four different kinds of molecules arranged in a line along a chromosome and that they “unzip” and “rezip” to create a new formula for a human body in the process of meiosis. I’ve got the thing about how they’re arranged in a double helix. Now I learn the epigenes are molecules that the doubled helix wrap around, as well as forming a kind of sleeve. These molecules are so small that the substitution of a single atom in the molecule will change its “shape” and that will change the way the joined molecules in the main double helix will operate: turn them up, turn them down, turn them off, turn them on.
Most amazingly, epigenes can be changed by the environment, part of which is the culture. The environment changes, the culture changes, the action of the epigenes change which changes the “expression” of the genes, and this is inheritable, at least for a few generations. There is an expectation that the influence of the different epigenes will fade over time, but this is not tested. Things that can change the expression of the genes include: starvation, generous over-eating, smoking, alcohol, high dosage vitamins, and substances rubbed onto bodies, like baby oil or shampoo. It is suggested that the widespread (and sometimes deadly) peanut allergies are due to peanut oil in baby oil. In my generation baby oil mixed with iodine was the sun lotion of choice.
An article in Time magazine, January 18, 2010, is my chief source this morning and it’s much clearer than the account I’ll be able to outline, partly because “John Cloud,” the author was working with an editor and a different kind of time frame. He begins with research by Dr. Lars Olov Bygren, a Swede, working on data from the 1800’s in the far north country where crop failures alternated with crop surpluses and the people evidently had no means of compensating, so that some years they starved to death and literally the next year they ate as much as they could. Dr. Bygren chose 99 persons born in 1905 and studied them in terms of their parents and grandparents who went through those erratic food supply years. It was already known that women who were terrified or malnourished during the time they are carrying their babies would hand on a vulnerability to heart attacks. But this was different. The children and grandchildren of both men and women who passed through that severe feast or famine sequence lived an average of six years shorter.
One of the mysteries about how a body works is that every cell in it has the very same DNA and yet one cell turns out to be part of a bone in your foot and another part turns out to be a spongy oxygen-permeated bit of lung tissue. How does it know which to be? Evidently the epigene carries that information, especially during the development of the embryo in the first place. It’s as though the genes were a huge million-keyed concert pipe organ, and the epigene were the fingers pressing the keys to make music. Every note is there in potential, but the timing and sequence is not in the keys.
On GNXP.com I kept reading about “methylation,” and now I learn that methyl is a basic chemical recipe: one carbon attached to three hydrogen atoms. Methylation is how the finger comes down on the key. A relevant experiment is one done on “agouti mice,” which are ordinary mice with a mutation that makes them yellow and hugely fat. They are not a different species, but a regular mouse with an altered gene. (If you Google, you’ll see vivid photos.) But if these mice were fed a special diet packed with B vitamins (folic acid, which seems so crucial to gestation, and B12), they turned out brown and normal-sized. Somehow they either normalized the gene or compensated for the mutation.
So the scientists are now busy inventing methyls that will cause strange effects. (Fruit flies with outgrowths of eyes that will last through the next 13 generations. Or roundworms that look dumpy and switch off a green flourescent protein for the next 40 generations.) One paper lists 100 of these consequences of epigenes that carry over for multiple generations. The next step is methyls that will “cure” diseases due to genes.
On another blog (www.swanrivermanitoba.blogspot.com) I’m posting photos of my father’s family from the early 1920’s when they were growing potatoes in northern Manitoba after decades of doing the same thing in South Dakota. In the photos my grandmother is developing a goiter, which is a consequence of not getting enough iodine in one’s diet. The thyroid gland in the neck, which controls metabolism and probably affects the other endocrine glands, swells up. The same condition killed Charlie Russell a few decades later. But somehow my grandparents were able to find “a woman” who knew to prescribe iodine in tiny amounts and also, I suspect, recommended a move to the West Coast where there is a lot of iodine in the garden soil and especially in ocean fish. By the time I knew her, she looked quite normal without any surgery. But I will now begin to look for the epigenomic consequences of iodine deprivation.
I’m Scots-Irish on both sides so my genes evolved over the years to suit the acid, iodine-rich environment of those sea islands. They were unsuited to the alkali low-iodine inland prairie, but I’m sure that my nutrition-conscious mother put enough cod liver oil down us to compensate. Anyway, we were in Portland, Oregon, and my father in his travels brought home salmon and crab. We dipped smelt and dug clams.
A period in human life that is sensitive to epigenetic influences is the onset of puberty, the switch-on of the sexual endocrine organs that floods the body with new molecules. A study looked at boys who began to smoke before age eleven, and discovered that their descendants were fat, vulnerable to diseases that will shorten their lives. I visualize them as agouti mice. Think of all the men who smoked their way through WWII. Fifty years, or a little more than two generations later, are we becoming a nation of agouti mice? So many questions, so much vulnerability to things over which we had no control in the past, but which will greatly affect the children of the future.