A factor or mechanism that changes the expression of a gene or genes without changing their DNA sequence. The effect of this is to change a phenotype without changing the genotype.
Epigenetic factors are very important during development - guiding the differential expression of genes in different cells. Mechanisms include DNA methylation and chromatin remodelling. When particular epigenetic processes are disordered, particular dysmorphic syndromes (for instance Angelman and Prader-Willi syndromes) and cancers can result because the usual expression of certain genes has been changed.
