After testing, S0 mice were selected for breeding based on their preference for 10% ethanol. The 20 males and 20 females with the highest preference values were paired, with brother–sister matings avoided, to create a ‘high’ preference line; similarly, the 40 mice with the lowest preference scores were paired to create a ‘low’ preference line. Approximately 200 pups from each generation were weaned and tested at adulthood as described above for three subsequent generations; active selection concluded at S3. S4 alcohol-naive pups were used for genetic analyses.
