Literature classes can teach students to read between the lines, to understand how prose is built beyond the simple linking of nouns and verbs. The same critical reading skills are required for geneticists to understand how the genome is more than just a long string of letters called DNA. Rather than reading between the lines, geneticists read above the line in an emerging field called Epigenetics.
To keep a thread from becoming a knotted mess, a seamstress keeps the strands wrapped around a single, large spool. To keep DNA from becoming tangled, cells wrap the DNA strand around proteins called histones. Rather than using one large spool, cells wrap the DNA around multiple histones creating a beaded necklace, with histones as the beads and DNA as the chain. Those histones are more than just simple spools or decorative beads, though. The structure of those proteins can be altered through the addition and removal of certain chemical groups. The presence or absence of these alterations is referred to as the epigenetic code because it is genetic information contained "above" the DNA sequence. Alterations change which portions of the DNA are easily accessible by the cell and which portions are too tightly wrapped up for the cell to read. If the cell cannot read, or can too easily read, certain portions of the DNA, then the way the cell uses information written on that portion of DNA will change.
Alterations of histone proteins occur at any stage of an individual's life. Investigating what sorts of stimuli can create those changes and characterizing the results of those changes is the pursuit of Epigenetics. Research investigating the role of exposure to environmental toxins during gestation has previously indicated that a component of anti-stick coatings like Teflon is correlated with increased rates of obesity in those children when they become adults. A separate study linked exposure to that same environmental toxin to changes in the histone modifications of newborn infants. Additionally, resent research
indicates the diet and chemical exposure of mothers before and during
pregnancy can alter the epigenetic sequence of her offspring, thereby
increasing her children's changes of being diagnosed with
obesity-related diabetes. Combining studies of the health effects of environmental toxins with studies of the epigenetic changes caused by those toxins may help investigators explain why certain toxins have certain effects.
Other elusive biological questions of interest to Epigeneticists include why inheriting a certain gene from one parent rather than the other can produce different effects, the causes of diseases including schizophrenia and colon cancer, and why identical twins are not perfectly identical.