Figure 1. Types of Epigenetic Information and Epigenetic Inheritance

A, Types of epigenetic information. The term epigenetics refers to modifications of DNA or associated factors—aside from variations in the primary DNA sequence—that carry information content and are maintained during cell division. Examples of epigenetic modifications are DNA methylation, histone modifications, occupancy of chromatin factors, and changes in chromatin structure. CTCF indicates CCCTC-binding factor. B, Inheritance of DNA methylation. In somatic cells, epigenetic information is replicated during mitosis along with the DNA sequence. The mechanism for replication of DNA methylation is well understood but the mechanism for replication of histone modifications is not.