What does the term "epigenetic change" refer to?

The term "epigenetic change" refers specifically to stable alterations in the chromatin structure that affect gene expression without altering the underlying DNA sequence. These changes can involve various modifications, such as DNA methylation and histone modification, which can influence how tightly or loosely DNA is packaged in chromatin. This packaging affects accessibility for transcription machinery, thus determining whether genes are expressed or silenced.

Unlike transcriptional changes that may occur as a direct response to stimuli or conditions, or mutations that involve changes to the DNA sequence itself, epigenetic changes can lead to long-term effects on gene activity even when the DNA sequence remains unchanged. They can also be heritable, meaning they can be passed down to subsequent generations, which introduces an additional layer of complexity in inheritance patterns beyond classical genetics.

Overall, the concept of epigenetic change emphasizes the dynamic interplay between genes and their expression mechanisms, contributing to the regulation of developmental processes and responses to environmental factors.