Which of the following is not an example of epigenetic change?

Epigenetic Modifications - This is a mechanism that results in stable propagation of gene activity states from one generation of cells to the next. The epigenetic modifications include changes in histones and DNA methylation. Epigenetic states can be modified by environmental factors which may result in the expression of abnormal phenotypes. These epigenetic modifications control gene expression and changes are also inherited. The epigenome is represented by methyl groups attached to DNA base cytosine and ceain covalent modifications in histones. Ref: DM VASUDEVAN'S TEXTBOOK OF BIOCHEMISTRY,SIXTH EDITION, PG.NO.,511.