Epigenetics is when the environment, or in this case, behavior and consumption of alcohol can change DNA expression. In itself, it does not affect gametes, it is simply a change in expression (it becomes available to transcription proteins). Part of the discussion describes how some people may be more suceptible to these DNA expression changes, and may explain hereditary addiction. Possibly it is a mechanism to keep the brain in homeostasis.
Chromatin unravels at a particular gene involved with anxiety, leaving it susceptible to protein-gene interaction (change in dna) and priming the brain for continued alcohol use and dependence.
HurpDurp54 OP t1_it0b5v8 wrote
Reply to comment by curious_geoff in Low doses of alcohol play a role in epigenetics and changes within the brain by HurpDurp54
I believe they did a trial with that as well, you'll have to search through the paper.