n. A gene that causes fruit flies — and perhaps humans — to more readily succumb to the effects of alcohol.
Flies, like humans, show telltale signs of drunkenness: first hyperactive and disoriented, then uncoordinated and sedated. Cheapdate mutants show inebriation at lower doses of ethanol, suggesting a lower tolerance for the drug.
—Robert Mitchum, “Kitchen pest is science's hero,” Chicago Tribune, March 06, 2009
A team led by Dr. Ulrike Heberlein of the Gallo Center at the University of California at San Francisco created thousands of fruit flies with genes randomly knocked out. One of the flies couldn't hold its alcohol. They dubbed its genetic flaw "cheapdate."

The researchers put flies inside a 4-foot glass dome — called an inebriometer — and pumped in alcohol vapor. The dome is crisscrossed with mesh landings. Ordinarily, the flies like to stay near the top. But as they got drunk, they fell from level to level.

Ordinary fruit flies take 20 minutes to hit bottom. But the cheapdate mutants tumbled down in 15 minutes.
—Daniel Q. Haney, “Buzzed flies hold clue to why we get drunk,” Chicago Sun-Times, June 12, 1998
1998 (earliest)
Upon exposure to ethanol, Drosophila display behaviors that are similar to ethanol intoxication in rodents and humans. Using an inebriometer to measure ethanol-induced loss of postural control, we identified cheapdate, a mutant with enhanced sensitivity to ethanol.
—Monica S. Moore, et al., “Ethanol Intoxication in Drosophila: Genetic and Pharmacological Evidence for Regulation by the cAMP Signaling Pathway,” Cell, June 12, 1998
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