Some scientists suspect that the effects are passed down via so - called epigenetic changes, chemical modifications of DNA that can turn genes on or off. (sciencemag.org)
The first step was to locate the switches by analyzing specific chemical modifications on the DNA and the proteins that it wraps around. (scientificamerican.com)
In a bulk material, most of the atoms are buried under the surface and are inaccessible for chemical modification. (cen.acs.org)