Epigenetics is the study of how gene expression can change without a change in the DNA sequence. In addition to DNA, proteins called histones are part of the chromosomes. The DNA wraps around these proteins. Chemical tags cover the histones and the DNA. This layer of structure makes up the epigenome, and it is what gives the genome its physical shape. The epigenome is able to change the accessibility of certain genes by either tightly coiling around them, making them unreadable, or relaxing them, making them easier to read. These changes in structure change the phenotype of the organism, or the physical trait that the gene expresses (Genetic Science Learning Center). The changes can also affect the production of proteins in cells so that the cell only produces the specific proteins that it needs (“What is Epigenetics?”). …show more content…
DNA methylation is one of the most well known mechanisms. This is when a methyl group is added or removed from the DNA. It often happens in places where cytosine bases occur consecutively in the DNA sequence (Weinhold). Chromatin modification is another epigenetic process. Chromatin is the complex of DNA and histones bundled tightly together so it can fit in the nucleus. Substances like enzymes, acetyl groups, and some RNA can modify the chromatin, which then alters gene expression. If a gene needs to be not expressed, the chromatin will be tightly folded up. Open chromatin allows a gene to be expressed (Weinhold). Processes like methylation and chromatin modification can cause a process called imprinting. Imprinting is when one of the two alleles in a gene pair is silenced through epigenetic processes. If imprinting occurs and then the expressed allele become damaged, problems can arise