Epigenetics Explained

Epigenetics has become one of the hottest specialties in biological science. It's a genetic phenomenon that has powerful effects on each of us throughout our lives, and it may even explain how we transmit genetic "memories" of our life experiences to our children, grandchildren, and great-grandchildren. But epigenetics is not the end-all of scientific understanding or the answer to every health questions.

A Workable Epigenetics Definition

What is epigenetics, anyway? If you were to read most articles on genetics, even some written by genuine scientists of genuinely respected credentials you might conclude the definition is something like this:

• Epigenetics explains why identical twins aren't completely identical.
• Epigenetics explains that my great-grandmother's struggle to get food in World War II is the reason I'm fat now.
• Epigenetics explains why some people can't help cheating on their spouses.
• Epigenetics explains why I got lung cancer, not my smoking.

In short, epigenetics is often used as an explanation for (1) things that we just don't understand or (2) things we don't want to blame on something else. But at least on a biological level, epigenetics is something entirely different.

Epigenetics Is Information Overlaid on DNA

Epigenetics is basically additional information added to DNA. If you thought of DNA as an instruction manual, epigenetics would be the highlighted sections of the text. A user could highlight important sections in red and less important sections in blue, as if to say, "Be sure to follow this," but "Don't pay as much attention to that." Those highlighted sections stay with the text even if the book is photocopied, although the colors may not come through. 

Something similar happens with DNA. Every cell in our body has the same sequence of A, C, G, and T bases, but not every cell does the same thing. DNA in the strand can be tagged with methyl groups (-CH3) that attach themselves to the "C" (cysteine) bases. This process is known as DNA methylation. Methylation is like the blue highlighter in the instruction manual, telling the user "You don't need this right now."

Epigenetics and the Histones

Have you ever wondered why DNA is coiled like a helix? Or how it stays that way?

Another set of actors in epigenetics are the histones. These are proteins that act as a kind of spacer between the strands of DNA. Together with DNA they make up microsomes, which look something like strings of pearls under electron microscopy.

Histones attract methyl groups. Because DNA is helical, sometimes this makes a segment of DNA more exposed. This in effect activates a gene. Sometimes it makes a segment of DNA less exposed. This in effect deactivates a gene.

Turning genes on and off makes sense in terms of cellular function. A brain cell, a fat cell, and a muscle cell all have the same DNA, for instance, but they don’t have the same functions. Different genes are activated in the different kinds of cells.

READ Non-Exercise Activity Thermogenesis - A NEAT Way To Stay Trim

Turning genes on and off also makes sense in terms of life history. If your grandmother nearly starved in World War II, even if you were born in 1985, your genes for fat storage may be turned on in 2016. Your DNA prepares gives you a head start on dealing with your environment, although your genes may not get the message that your world is different from your grandmother’s.

Epigenetics explains how we are pre-programmed to deal with changing life conditions. Your DNA stays the same throughout life, but different parts of it are activated or deactivated.

How Epigenetics Makes a Practical Difference in Your Life

Just about any outside stimulus, an infection, a chemical, a life experience, or even an emotion, has the potential to make an epigenetic change in your DNA. The precise ways certain life experiences change which genes are activated and which genes are not is still poorly understood, but there is mounting evidence for epigenetic changes caused by several common experiences.

• Exercise has been known to be beneficial for decades, but only since 2000 have scientists begun to understand that exercise marks DNA not just in muscle but also in fatty tissue.
• Childhood abuse causes lifetime changes. Some of them are even encoded into DNA.
• Bisphenol A (BPA) is a chemical added to plastic that is known to interfere with the action of sex hormones, to accelerate deposition of fat, and to increase the risk of cancer. Some of its effects are the result of DNA methylation that causes epigenetic changes.

There is a widely accepted body of evidence for epigenetic changes that happen during the lifetime of an individual. There is less evidence for passing epigenetic changes from grandparents to parents to children.

• Much of the early study of epigenetics concerned the agouti gene. Both normal-weight brown mice and yellow obese mice can have the same gene (or genotype) but very different outward characteristics (or phenotype) depending on whether this gene has been methylated. Folic acid is a source of the methyl groups that act on this gene. If the mother mouse gets more folic acid, her pups will tend to have brown coats and to be normal weight. If she gets less folic acid, her pups will tend to have yellow coats and to be obese.
• Studies of prairie voles (a kind of field "mouse") in Florida have found that when DNA in brain cells in the animal’s nucleus accumbens, a kind of traffic control center in the brain, are methylated, the animal mates for life. As long as the DNA in these cells is not methylated, it literally and figuratively “plays the field.”
• Many people scoff at the idea that marijuana is a gateway drug. However, there is a growing body of evidence that smoking marijuana during adolescence activates a gene that increases the likelihood of heroin addiction in adulthood.

READ Can't Fit Into Your Jeans? The Reason May Be Your Genes

• Studies of survivors of famine in Sweden and in the Netherlands have found that epigenetic activation by starvation can be passed down for at least three generations. It’s a very common observation that people who survived starvation in World War II and other conflicts of the twentieth century tend to have weight problems once they can get normal amounts of food again, and their children and grandchildren tend to have weight problems, too. Research is ongoing to figure out how to deactivate these genes that set the stage for obesity.

Studies of over 1,000 patterns of epigenetic activation in humans are underway, but it’s too early to generalize their results. However, medical science is finding more and more significance for methylation, and for folic acid metabolism, every year. Just don’t assume that more folic acid is always better, at least not yet.