As in a mutation of the DRD2 gene that is frequently associated with alcohol addiction or the expression of CHRNA2 that has been implicated in nicotine dependence? A decreased number of D2 dopamine receptors seems also involved in a predisposition for addiction.I wish that scientists doctors etc could Identify an "addiction " gene or figure out why some go off the rails. I had an english teacher in high school that smoked for 10-15 years. She up and decided to quit, no patch, no therapy nada.