Photos by Scott Cunningham
Most of us have a very basic understanding of how genetics work.
If you have brown eyes, you know that color was determined by your parents’ DNA. Perhaps you can point to a photo of a great-grandmother on your father’s side and say that’s where your red, curly hair came from.
These genes “run in the family,” says Jay Hollick, associate professor of molecular genetics at The Ohio State University. DNA is a blueprint – a guideline – that helps create who we are.
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While our DNA is passed down to us at birth, our gene expression may be influenced by the present day. What if our unique decisions – whether or not we eat breakfast, go for an evening jog or live in a heavily polluted city – can influence not only our own genes, but possibly the genes we pass along to our future children and grandchildren?
Epigenetics is the study of changes in organisms (mammals and plants) caused by changes in gene expression, rather than changes in the genetic code itself.
Or, as Hollick explains, some of our traits are determined by information that is independent of DNA, but can still be copied and transmitted through cell divisions.
Picture this: “Let’s eat Grandma” is the information encoded in the DNA. But when you add a comma – or the epigenetic mark that alters the DNA’s instructions, for the sake of this example – the message is changed entirely: “Let’s eat, Grandma.”
“Unlike DNA, which is a remarkably stable form of information, epigenetic sources of information are often unstable, and they may behave in an unexpected fashion,” Hollick says.
Another example would be body parts such as skin, eyes and teeth. Your skin, eyes and teeth all share the same DNA, and genetically you can’t tell them apart, but their cell types perform very different functions.
The concept of epigenetics might not be as new as you think. Hollick says inheritance patterns of specific traits that don’t fall in line with how DNA operates have been noted for more than 100 years. The term “epigenetics” was coined in 1942 by fruit fly geneticist and developmental biologist Conrad Waddington.
There are plenty of aspects of epigenetics that are still the subject of much debate, such as whether the environment has any impact when it comes to inheritance of traits in mammals.
In plants, Hollick says, sperm and eggs are produced well after the plant has been subjected to any environmental insults. So, while few clear examples exist, plants can transmit a memory of that experience to their offspring.
But in mammals, sperm and egg precursors are set aside early in fetal development. Their exposure to the environment is limited to in utero.
“Several epidemiological and animal model studies provide support for the idea that under-nutrition during gestation results in heritable consequences to the metabolism of offspring and grandchildren,” Hollick says. “So, it is certainly an issue in need of more investigation.”
To give an example, it could very well be possible that someone who can’t gain weight easily might have had a malnourished ancestor.
There’s still a lot that can be learned about epigenetics, like how specific instructions in the DNA of individual cell types are either interpreted or ignored, Hollick says.
“We still have much to learn about these fundamental processes occurring during development and in response to environmental influences,” Hollick says. “The sources and behaviors of epigenetic information inherited from one generation to the next are less well understood, partly due to the experimental requirement for well-pedigreed materials.”
Hollick says more information is also needed to understand how proper nutrition and exposure to pollutants, drugs and alcohol affects epigenetic processes.
“Whether or not the environment is responsible for heritable changes in health and agriculture is certainly an important concern for our future well-being,” he says. “We should be investing in the research and tools needed to understand the extent of this connection.”
Hannah Bealer is an assistant editor. Feedback welcome at ssole@cityscenemediagroup.com.
