Epigenetics refers to differences in the body's phenotype caused by chemical regulation of genes in the DNA. Changes that may be heritable, but do not change the overall DNA sequence. Genes can either be activated or repressed by protein regulators known as transcription factors. Changes conceptualized as “above genes.” Genes are sections of the DNA sequence, and chemical imprints can be permanently placed on them, effectively modifying the meaning of the gene without changing its actual language. The imprint itself is then controlled (turned on & off) by proteins, and the various signals are recorded in the epigenetic tag, subsequently creating highly sophisticated genome databases.
How? Well, if you were to read a DNA sequence in a continuous line, whenever you come upon a gene with an epigenetic tag it would either be readable (expressed) or un-readable (repressed). Readability is determined by the tag placed on it by regulatory proteins, i.e. allowing the gene to produce proteins if expressed, and consequently not allowing the gene to produce proteins if repressed. Transcription factors bind to the promoter site of the gene (usually where RNA attaches in order to copy the gene’s instructions in order to create the coded protein). These transcription factors can either act as repressors (meaning they block the promoter site), or expressors (meaning they activate the promoter site, maybe even helping the RNA bind to the promoter site). Why? Well, genes can be either expressed or repressed in order to regulate the human body, making sure that genes are working harmoniously, and producing the correct proteins at the correct times. Remember the genes can be toggled back and forth from, expressed to repressed. Similar to a switch, proteins turn genes on and off. For example, say the body needs more of a certain protein that is produced by a certain gene, a signal will tell the regulatory proteins to turn on that particular gene which will start protein synthesis as needed and when the need is satisﬁed regulatory proteins will turn that particular gene off again.
Epigenetic marks may even be inherited through transgenerational epigenetic inheritance. The human genome even has detectors that recognize viral genes and silence them immediately with epigenetic markers, this is an ancient genotype defense. Epigenetics can even record injuries suffered or diseases surpassed. In the human body there are around 21,000 genes, some organically have epigenetic markers, but the more interesting of the lot are genes tagged by epigenetic markers because of environmental factors (an exterior inﬂuence).