Epigenome

 The Epigenome is a combination of many chemicals/proteins that are used to suppress or express (control) certain genes in a genome ⁽¹⁾ . They maintain control of the genome by the use of methylation and the particular properties of histones ⁽¹⁾ . Unlike the Genomic of organisms, epigenomic modification isn’t permanent allowing more adaptivity and flexibility to new environmental and lifestyle ⁽²⁾. Epigenomic modifications don't physically change the genetics of the organism but like genomics, can be passed down for many generations ⁽¹⁾. Alteration of the epigenome is mainly seen in specialised cells to make them efficient in their function (this is done so by the process of deactivating/reactivating gene sequences in the genome)⁽¹⁾.

Influencers of the Epigenome

• The DNA of an organism is compacted into the cell using histones ⁽¹⁾. Histone influence epigenomics by modifying the degree of expression/inhibition of a specific gene depending on the tension of the DNA around them. DNA that is wrapped tighter around the histones has a more inhibitory factor of gene expression due to the genes being unavailable to modify leaving them in a deactivated response. Genes that are loosely wrapped histones are open for modification by methylation and so are often activated and deactivated due to environmental stimuli
• Methylation is the "switch" function of epigenomics. This is due to the methyl group joining to the histone/gene forming an epigenetic tag on it cause the total activation or deactivation of the gene ⁽²⁾. These tags bind to the promoters of some influencing an inhibitory response preventing further transcription of the gene ⁽²⁾.
  

References:

1. National Human Genome Research Institute, Epigenomics, April 1st 2016, citied 16th November 2017, https://www.genome.gov/27532724/epigenomics-fact-sheet/
2. Nature Education, Epigenomics: The New Tool in Studying Complex Diseases, 2008, citied 16th November 2017, https://www.nature.com/scitable/topicpage/epigenomics-the-new-tool-in-studying-complex-694#