Any process that alters gene activity without changing the DNA sequence, and leads to modifications that can be transmitted to daughter cells. Includes methylation, chromatin modification, acetylation, phosphorylation, ubiquitylation, and sumolyation.
Epigenetic change is a regular and natural occurrence but can also be influenced by several factors including age, the environment/lifestyle, and disease state. It can result in diseases like cancer. At least three systems including DNA methylation, histone modification and non-coding RNA (ncRNA)-associated gene silencing are currently considered to initiate and sustain epigenetic change.