Chromatin domains and function

The inheritance of biological traits involves not only the transfer of genetic information in the form of DNA, but also epigenetic information. The latter is encrypted in a DNA component, methylation of cytosine residues, and in non-DNA components such as histone modifications, non-histone proteins, and RNA. Chromatin comprises both genetic and epigenetic information. The chromatin state determines which gene will be expressed, at which stage and in which cell. This concept forms the basis for cell differentiation during the development of a eukaryotic organism. It entails a high flexibility of chromatin with respect to molecular composition, biochemical modification, and physical organization. Indeed, chromatin is highly dynamic, showing continuous changes at different levels of organization and occupies different subdomains of the nucleus, each with specific functions. In this chapter, an overview will be given of chromatin states and nuclear domains in which chromatin resides.