Is alcoholism a genetic disorder?

Very often yes. Alcoholism does have a very strong genetic component, there is much research to indicate that many alcoholics brains are different than non, even before their first drink, however the degree of genetic influence would very between persons. The environment or life circumstances however are also part of the disease's expression. It is usually a combo of nature and nurture.
Heredity: 1 parent. Who's alcohol dependent means 34% more risk, 2 parents means 4x more risk, & 2 parents & grandfather means 9x more risk for a male. Environment: if everyone around you drinks, if drinking is considered respectable or expected, if you have lots of stress or emotional problems, or you self-medicate w/ alcohol, you are more likely to drink excessively. Longer habits become stronger & --> addiction.