Addiction genetics is a scientific fact. There is a reason Native's are known and prone to alcohol addiction.
The short of it, during meiosis (the splitting of genetic cells to contain only one set of chromosomes instead of two, creating eggs or sperm), there are these "tails" off the sides of DNA that lose bromine attached to them (bromination allows a segment of DNA to open up a gene for transcription and translation). Somehow, bromine re-attaches to the same tails and opens up the genes it unattached from in both the two new cells.
At which point the sperm and egg carries genetic information on to a new vessel. Think of it similar to instinct. How did those animals understand the same thing their parents did without being taught? How is sex drive instilled into pretty much everyone?