Scientists have been examining the potential of epigenetics at explaining non-genetic heredity. Epigenetics is the phenomena whereby phenotypic traits are controllably expressed or suppressed. That is, genes are either activated or deactivated. A typical example of this is in difference between cell types such as skin cells and liver cells; both contain exactly the same genetic information, but their specific epigenetic information causes them to structure and function differently. Such epigenetic differences may even be expressed at specific stages of development or under specific environmental conditions.Scientists have now shown that epigenetics is responsible for heritable characteristics not explicitly expressed in the DNA. Scientists have used a certain laboratory strain of the fruit fly Drosophila melanogaster with white eyes. The flies are normally nurtured at 25 degrees Celsius. However, if the temperature is momentarily raised to 37 degrees Celsius, the flies hatch with red eyes. The flies were then crossbred, and across 6 generations it was found that the phenotype was carried across despite the DNA of the eye colour gene being identical.
Histones have been implicated as the molecular structure responsible for the pattern of epigenetics. Histones have been typically shown to be a packaging material for DNA. However, the histones are also responsible for activating or deactivating genes, based on whether they are acetylated or methylated. These markers have also been shown to be a form of cellular memory. That is, that they are carried across cell divisions.
It is still uncertain how the histones survive cellular division. Furthermore, the influence of the environment is also under investigation, such as the effects of diet on epigenetics. This area of research has strong implications for environmental influences on genetics.
http://www.sciencedaily.com/releases/2009/04/090412081315.htm
http://www.newscientist.com/article/mg19926641.500-rewriting-darwin-the-new-nongenetic-inheritance.html
