The role of epigenetics in mediating environmental effects on phenotype.

Epigenetics is being suggested as a possible interface between the genetic and environmental factors that together give rise to phenotype. In mice there exists a group of genes, known as metastable epialleles, which are sensitive to environmental influences, such as diet, and undergo molecular changes that, once established, remain for the life of the individual. These modifications are epigenetic and in some cases they survive across generations, that is, through meiosis. This is termed transgenerational epigenetic inheritance. These findings have led to the idea that similar processes might occur in humans. Although it is clear that the lifestyle of one generation can significantly influence the health of the next generation in humans, in the absence of supporting molecular data it is hard to justify the notion that this is the result of transgenerational epigenetic inheritance. What is required first is to ascertain whether genes of this type, that is genes that are sensitive to the epigenetic state, even exist in humans.