Epigenetics—Inheriting More Than Genes

grandmas hand baby foot

The Science of Epigenetics is Forcing Scientists to Rethink their Assumptions

by Dr. Georgia Purdom

All our lives, we’ve heard that our physical makeup is determined by our genes, not environment. But the science of epigenetics is forcing scientists to rethink their assumptions.

You’re probably familiar with the phrase, “You are what you eat.” But did you know that you are also what your mother and grandmother ate? The budding science of epigenetics shows that our physical makeup is about much more than inheriting our mother’s eyes or our father’s smile.

We are accustomed to thinking that the only thing we inherit from our parents are genes—packets of information in DNA that give instructions for proteins. These genes determine our physical traits such as hair and eye color, height, and even susceptibility to disease.

But we also inherit specific “modifications” of our DNA in the form of chemical tags. These influence how the genes express our physical traits. The chemical tags are referred to as “epigenetic” markers because they exist outside of (epi-) the actual sequence of DNA (-genetics).

Let me use an analogy to explain. The following sentence can have two very different meanings, depending on the punctuation used. “A woman, without her man, is nothing” or “A woman: Without her, man is nothing.” Perhaps it’s a silly illustration, but it gets the point across.

The words of both sentences are the same, but the meaning is different because of the punctuation. The same is true for DNA and its chemical tags. The sequence of DNA can be identical but produce different results based on the presence or absence of epigenetic markers. For example, identical twins have the same DNA sequence but can have different chemical tags leading one to be susceptible to certain diseases but not the other.

Parents can pass down epigenetic markers for many generations or their effect can be short-lived, lasting only to the next generation. Either way, the changes are temporary because they do not alter the sequence of DNA, just the way DNA is expressed.

What does this mean in practice? Your behavior, including the food you eat, could change how your body expresses its DNA. Then those changes—for good or bad—could be passed to your children! If you do something to increase your susceptibility to obesity or cancer or diabetes, your children could inherit that from you.

In one experiment, mice from the same family, which were obese because of their genetic makeup, were fed two different diets. One diet consisted of regular food. The other diet consisted of the same food but contained supplements that were known to alter the chemical tags on DNA.

Normally when these mice eat regular food they produce fat offspring. However, the mice that ate the same food with the supplements produced offspring that were normal weight. The parents’ diet affected their offspring’s weight!

Scientists are still trying to understand the details. The epigenetic markers that were modified by the food supplements appear to have “silenced” genes that encourage appetite. The parents’ environment—in this case, the food they ate before becoming parents—affected the weight of their offspring.

Certain types of medicine have also been suspected of causing changes in epigenetic markers, leading to cancer in the offspring of women who took the medicine. For example, a type of synthetic estrogen prescribed to prevent miscarriages has been linked to an increased number of cancers in their daughters’ and granddaughters’ reproductive organs.

Studies point to changes in the epigenetic markers related to the development of reproductive organs, which the mothers passed down to their daughters. This finding affirms the adage that “you are what your mother—or grandmother—ate.”…