DNA Methylation in Mammalian and Non-Mammalian Organisms

Abstract

Of particular interest in biology is how different chromatin states contribute to the complex regulation of gene transcription that is necessary to establish and maintain multi-cellular organisms. This is because (with few exceptions) each cell within an organism contains the same genomic sequence, meaning that the diversity of expression states is not due to variability in the underlying genetic sequence but could result from differences in chromatin landscape. This area of research comes under the umbrella of ‘epigenetics’, which is concerned with molecular processes involved in regulating gene expression that are transmittable and independent of changes in DNA sequence. However, perhaps owing to the ambiguity of this definition, the term often means different things to different people. A more precise definition of 'epigenetic' mechanisms is 'the structural adaptation of chromosomal regions so as to register, signal or perpetuate altered activity states' (Bird, 2007). Differentiated cells are said to have an 'epigenetic memory' imparted by epigenetic processes that can maintain a pattern of gene transcription through time and cell divisions. Understanding the mechanisms involved in setting up and maintaining these processes is an exciting area of research investigation.