When I was first assigned this article, my immediate thought was, "Do I even understand epigenetics?" Not really! Pulling out my trusty dictionary and dusting off my old genetics textbooks yielded this delightful definition: the study of heritable changes in gene expression that occur without altering DNA sequences.

I obviously needed help. Three genetics experts immediately came to mind: George Seidel Jr., PhD, university distinguished professor at Colorado State University’s College of Veterinary Medicine & Biomedical Sciences; Carey Satterfield, PhD, an assistant professor in physiology and reproduction at Texas A&M’s College of Agriculture and Life Sciences; and Ernest Bailey, PhD, one of the University of Kentucky Gluck Equine Research Center’s immunogenetics and genomics researchers. These individuals shared their "best" definitions and examples of epigenetics and its impact on early fetal development. But before delving into these details, we’ll briefly review DNA and what genes do.

Decoding the Genetic Code

The term DNA is short for deoxyribonucleic acid. The "deoxyribo-" refers to a specific type of sugar, "nucleic" refers to the fact that most DNA is found in the nucleus of virtually every cell in an organism, and the "acid" refers to phosphoric acid. The deoxyribose sugar and phosphoric acid bond together and form the "backbones" of DNA–you could think of two chains of the bonded sugars as the two upright poles of a twisted ladder (at right). Bonded to each pole of the ladder like rungs are the genetic bases: adenine, cytosine, guanine, and thymine. These bases are usually represented by the letters A, C, G, and T. A base on one pole binds to a base on the other pole, forming the rungs. In essence, the presence and arrangement of these four compounds define our entire genetic code