How does epigenetic inheritance occur?

Epigenetic inheritance occurs through the maintenance of chemical modifications across generations without changes to the DNA sequence itself. A key example of this in mammals is "imprinting," where certain genes behave differently based on whether they are inherited from the mother or the father. These imprinted genes maintain their epigenetic states across generations, which means they remember their history of being from the mother or the father and behave accordingly 1.

Epigenetic inheritance can also involve changes that affect the organism's traits without altering the DNA sequence. These changes can be transmitted through chemical modifications, particularly methylation of cytosine, where a methyl group is added to cytosine in the DNA. This affects how genes are expressed. Additionally, histones, which are proteins that DNA wraps around, can also be modified by methylation, acetylation, and other processes to influence gene expression 2.

These epigenetic modifications can sometimes be passed down through generations, influencing traits in descendants without altering the underlying genetic code. However, during the transition between generations, a process called "epigenetic reprogramming" occurs where most of these modifications are erased, allowing the genetic material to start largely anew in the offspring, although a small percentage of modifications can sometimes remain 3.