epigenetics
n. the study of heritable chemical modifications to DNA that alter gene activity without changing nucleotide sequence. Such modifications instead typically involve the attachment of additional material to the DNA molecule itself (DNA methylation) or the structural alteration of its associated proteins (chromatin remodeling), which disrupt the normal development and functioning of cells by influencing gene activation, deactivation, transcription, and so forth. Epigenetic mechanisms have been proposed as the means by which environmental and psychosocial factors such as toxins and early childhood experiences interact with physiology: They affect neural function through changes in gene expression that lead to individual differences in cognition and behavior (e.g., learning, memory, aggression, affect). Research also suggests that some epigenetic changes of an individual can be passed down to more than one generation of descendants.
Additionally, epigenetic abnormalities have been linked to the etiology of many diseases and mental disorders, including autoimmune disturbances, cancer, heart disease, anxiety, autism, depression, intellectual disability, schizophrenia, and substance abuse.