14.10 : Epigenetic Regulation

Epigenetic regulation refers to changes in gene expression that can be inherited without changes to the genetic sequence. This occurs during the normal course of development and can also be caused by environmental factors, such as diet, exposure to toxic substances, and stress.

Epigenetic regulation occurs through three main mechanisms: DNA methylation, histone modification, and RNA-based processes.

In DNA methylation, methyl, CH3 groups, are added to specific bases. This alters the ability of regulatory proteins, such as transcription factors, to bind to DNA. Usually preventing the gene from being transcribed.

Histone modification involves adding chemical groups, such as methyl or acetyl groups, to the histone proteins that DNA wraps itself around to form chromatin. These modifications affect how tightly chromatin is folded. Either opening it up, making it more easily transcribed, or condensing it, inhibiting transcription.

Various types of RNA can also have epigenetic effects, including micro-RNAs and small interfering RNAs, which can alter chromatin structure. And messenger RNA, which can be methylated, altering gene translation.

Whatever the mechanism, these modifications are passed down to daughter cells, and sometimes even passed down through generations of individuals, creating long-term phenotypic changes without changes to the genome.