Telling genes what they are

By studying identical twins, scientists believe that inheritance is more complex than simply passing along the genetic blueprint from mother to daughter, father to son. The Economist:

It is not, however, enough for organisms to share DNA in order to sharecharacteristics. Those genes must also behave in the same way. One of the ways that the behaviour of genes is regulated is by the application to their DNA of particular clusters of atoms, known as methyl groups. Methylation shuts a gene down. To the extent that the pattern of methylation is passed from parent to offspring, it forms a second, 'epigenetic', inheritance mechanism parallel to the primary DNA-based one. The importance of epigenetic inheritance is now a matter of hot debate.

This idea has also been published recently in the SEED article, Extending Darwinsim, and it's an issue that I first picked up several months ago. Are there environmental factors at work in natural selection?


Wikipedia: Epigenetics