standard gene knockouts, over expression transgenics, and targeted point mutations, most expressed throughout development but some altered conditionally or in a brain region specific manner. These various manipulations of 23 genes increased preference drinking significantly; for 30 genes, preference was significantly reduced; and for 33 genes, no substantial difference from controls was seen. Analysis of this distribution yielded χ2 = 1.84, p = 0.4 (NS). Our interpretation of this pattern is that while a specific gene or gene pathway may well affect preference drinking when looked at in isolation, there are so many potentially influential genes that it is not easy to see how this oligogenic trait will yield its secrets to a one gene at a time analysis.
