ABSTRACT
The primary DNA sequence is only a foundation for understanding how the genetic program is read. Superimposed upon the DNA sequence is a layer of heritable “epigenetic” information, a facet of the genetic code that we have only just begun to discover and appreciate. Epigenetics is defined as “mitotically and/or meiotically heritable changes in gene function that cannot be explained by changes in DNA sequence” (1). This epigenetic information is stored as chemical modifications falling into two main categories: (1) DNA methylation and (2) changes to the histone proteins that package the genome (2). By regulating DNA accessibility and chromatin structure, these chemical changes influence how the genome is translated across a diverse array of developmental stages, tissue types, and disease states (3-5).
