Are Imprinted Genes Adaptive or Maladaptive?
Epigenetics is referred to be the study of heritable changes other than those in the DNA sequence that encompass two major modifications of DNA or chromatin: DNA Methylation, the covalent modifications of cytosine, and post-translation modification of histones including methylation that is a highly intricate process that occurs within each cell as well as supplying fluid in the brain and within the liver, acetylation , phosphorylation and sumoylation (Callinan and
Feinberg 2006) which is the is a post-translational modification involved in various cellular processes, such as nuclear-cytosolic transport, transcriptional regulation, apoptosis, protein stability, response to stress, and progression through the cell cycle . Epigenetics is the mechanism that leads to parent-of-origin effects via imbalanced expression of maternally and paternally inherited copies of a gene. It plays a role in several Mendelian diseases and there is growing evidence for its role in common diseases as well as cancer. It is a dynamic mechanism with varying degrees of monoallelic expression between tissues and developmental stages (Wolf et al. 2008;
Kong et al. 2009; Skaar et al. 2012; Lawson et al. 2013; Peters 2014). In addition, recent evidence suggests that noncoding RNAs predominantly microRNA contribute to the stock of epigenetic mechanisms that are found in major diseases and that can occur at critical developmental times
(Esteller 2011).

There are two types of genes are modified epigenetically: imprinted genes and genes with metastable epiallelles. Imprinted genes are those in which specifically either the maternally derived or the paternally derived allele is suppressed, thereby rendering them functionally haploid. In other non-imprinted genes, one or both alleles are regulated epigenetically, and these metastable