Define epigenetics.

Epigenetics refers to heritable changes in gene expression that do not involve alterations to the underlying DNA sequence. This means that while the genetic code remains unchanged, the way genes are expressed—how much of a protein is produced or whether a gene is turned on or off—can be modified by various factors such as environmental influences, lifestyle, and developmental stages.

These modifications can occur through mechanisms like DNA methylation, histone modification, and RNA-associated silencing. Importantly, these changes can be passed from one generation to another, affecting traits without changing the sequence of the DNA itself, which is a fundamental aspect of epigenetics. Thus, the essence of epigenetics lies in its ability to regulate gene expression through reversible modifications that can have significant biological implications, such as in development, disease, and phenotypic variation.