Correlated Responses of Different scute Genotypes to Long-term Selection for Increased Abdominal Bristle Number in Drosophila melanogaster

Abstract

The first dose effect of sc+ has been measured for abdominal bristle number in six replicate lines of D. melanogaster being selected upward for this character in the sc homo-and hemizygote. The within-line regression coefficient of the heterozygote on the sc homozygote showed considerable variation among the lines with a range of 0-47-1' 22, indicating the dependence of gene action on genetic background. But, on the average, the effect of sc+ was approximately additive for abdominal bristle number. From this average, the genetic correlation in the base population between the two genotypes was estimated to be considerably less than unity, which suggests some genetic variability that is dependent on the genotype of the major locus. A similar relationship was also obtained for the two male hemizygotes.