the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself.
Environmental factors, age and lifestyle can cause genes to be silenced or expressed over time. In other words, parts of the DNA sequence is read differently, being turned off or turned on dependant on environmental factors.
Analogy by Nessa Carey: “Think of the human lifespan as a very long movie. The cells would be the actors and actresses, essential units that make up the movie. DNA, in turn, would be the script — instructions for all the participants of the movie to perform their roles. Subsequently, the DNA sequence would be the words on the script, and certain blocks of these words that instruct key actions or events to take place would be the genes. The concept of genetics would be like screenwriting. Follow the analogy so far? Great. The concept of epigenetics, then, would be like directing. The script can be the same, but the director can choose to eliminate or tweak certain scenes or dialogue, altering the movie for better or worse. After all, Steven Spielberg’s finished product would be drastically different than Woody Allen’s for the same movie script, wouldn’t it?”