The term epigenetics refers to the idea that the phenotype of an individual (or of a cell) is affected by inherited factors beyond the sequence of the DNA code.
By processes such as adding methyl groups to specific locations in a DNA molecule--a reaction called methylation--the expression of the DNA can be regulated. Various experiences, such as exposure to certain chemicals or other stimuli, during the lifetime of an individual can cause methylation at certain locations in the DNA. Methylated regions are often transmitted to offspring, thus carrying the regulatory "imprint" to the next generation and beyond.
Chemical changes to a DNA molecule (or DNA histones) such as methylation are often called imprinting. Imprinted information can trigger or affect various disease processes. For more information on the basic idea of epigenetic imprinting and its role in disease, see our coverage of the topic in Chapter 34 of Anatomy and Physiology. Our new 7th edition (due out in a few weeks) will have an expanded web article (A&P Connect) linked to the text coverage.
A recent article in Science News tells us that researchers are far from figuring out how this imprinting by methylation works. To read more about the recent findings . . . and new questions raised by them. . . check out this article:
One study finds tissue-specific methylation signatures in the genome; another a similarity between identical twins in DNA’s chemical tagging.
Science News web edition : Sunday, January 18th, 2009