Photo by Scott Cunningham
Skinny Genes
Lifestyle can influence genetic makeup
The way we view genetics is rapidly changing.
Everyone has a basic understanding. Maybe green eyes come from your mother’s side, and freckles come from your father’s. These genes, as we call them, are family traits. They are parts of our identity that are passed down, generation to generation, to make up who we are.
Jay Hollick, associate professor of molecular genetics at The Ohio State University, describes genes as a blueprint, or a guideline, that helps create our identity.
But here’s something that might shake up the way you view genetics. Our DNA is passed down to us at birth, but our gene expression could be influenced by the present.
That begs the question: What if our unique decisions influence not only our genes but, possibly, the genes we pass along to our future children and grandchildren?
These decisions could be just about anything. Some examples include whether we eat a healthful breakfast or exercise as much as we should. Even the places we decide to live – such as a city with clean air, or one that’s heavily polluted – can impact genetics.
Epigenetics is defined as the study of changes in organisms caused by changes in gene expression, rather than changes in the genetic code itself.
Some of our traits are determined by information that is independent of DNA, but can still be copied and transmitted through cell divisions.
Here’s an example that might be a bit easier to digest: “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.”
Skinny Genes
“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.
Think about some of your body parts – skin, eyes, teeth. Did you know they all share the same DNA? Genetically, you can’t tell them apart, but their cell types perform distinct functions.
The concept of epigenetics might not be as new as you think. The term was coined in 1942 by fruit fly geneticist and development biologist Conrad H. Waddington. The inheritance patterns of specific traits that don’t fall in line with how DNA operates have been noted for more than 100 years, Hollick says.
But just because epigenetics has been around for a while doesn’t mean all the technicalities have been ironed out. 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.
Plants and mammals each have a different experience. In plants, Hollick says, sperm and eggs are produced well after the plant has been subjected to any environmental factors. So while few clear examples exist, plants can transmit a memory of that experience to their offspring.
In mammals, though, 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.”
What does this mean, exactly? To give an example, it could very well be possible that someone who’s naturally thin and, despite his or her best efforts, cannot put on weight had a malnourished ancestor.
Hollick says there’s still a lot that can be learned from epigenetics, such as how specific instructions in the DNA of individual cell types are either interpreted or ignored.
“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.”
If you’re wondering how proper nutrition and exposure to pollutants, drugs and alcohol affect epigenetic processes, Hollick says that information is still being researched.
“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 gbishop@cityscenemediagroup.com.
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