Abstract
Populations of Drosophila melanogaster were investigated for variation in structural Amy genes, coding for different electrophoretic variants, and regulatory genes that determine the tissue-specific production patterns of alpha-amylase in the midguts of adults and larvae. Analysis of strains homozygous for second chromosomes extracted from three cage populations of different geographical origin revealed a consistent nonrandom association between Amy and midgut activity pattern (map) variants of alpha-amylase in adults and third-instar larvae. The origin and maintenance of the linkage disequilibrium between Amy and map genes are discussed.