Answer:
Histone acetylation or DNA methylation.
Step-by-step explanation:
The epigenetics may be defined as the genetic phenomena that might cause mutation in the organism's genome. The DNA sequence of the organisms do not get changed in epigenetics.
This phenomena is limited whether the gene is herited from the mother ot the father. The phenomena like acetylation of histones increase the gene expression. The DNA methylation and histone deacetylation at specific residues reduces the gene expression.
Thus, the answer is histone acetylation or DNA methylation.