Review of epigenetics

Epigenetics refer to 
Hence, while no structural change, there are functional alterations; according to Magge(2017), for some conditions identical twins can be discordant and these can be attributed to epigenetic modifications \cite{28060197}.  You can search Google to find more instances. 
Study the following table.
Table of Epigenetics
Condition Epigenetic Modification
XXX Long tail RNA
YYY Methylation