There is this recent study:
A gene mutation for excessive alcohol drinking found, although it used rats has its subject.
More informative was the following comment discussing a related study in light of the study's findings:
"We examined these polymorphisms very carefully, using a variety of sophisticated techniques which allowed us to detect not only any individual SNP effects that may exist, but also any effects that may exist in aggregate, across multiple SNPs in a given GABA system gene, and even the combined effect of all the GABA system polymorphisms we studied put together!
We found that there was no consistent association between any GABA system polymorphisms, either individually or in aggregate, and any measure of alcohol use or alcohol-related psychopathology.
...
What's certain, however, is that in the long run any single polymorphism will not be a strong and reliable predictor of alcohol use and abuse in either rats or humans (with a very few notable exceptions, such as a polymorphism in the ALDH2 gene which can cripple the body's ability to metabolize alcohol, but which is only prevalent in East Asian populations).
After decades of candidate gene studies like these, and more recently genome-wide association studies, it has become absolutely clear that
genetic influences upon alcohol use, abuse, and dependence, like nearly all complex behaviors, are the result of many, many polymorphisms, each of which has at most only a tiny individual effect, and, further, that these polymorphisms interact with each other and with the environment to produce alcohol-related behaviors. As a result, it is very difficult to consistently show that any single polymorphism is even associated with alcohol-related behaviors, much less strongly related and predictive of such behaviors."
Comment here.
So there may be a genetic link to alcoholism, but it will not be a simple, direct, or easily predictable one.
It should be pointed out that the scientific process rarely
proves things, but rather rejects or fails to reject stated hypotheses. When enough experiments support the hypothesis, it is then taken as fact; however, it has not been proven and may be discarded later in the face of new findings.