Restriction endonuclease map variation and gene activity in the Adh region in a population of Drosophila melanogaster.

Variation within a 12 kb region containing the Adh gene was studied in 16 highly inbred lines of independent extraction from a population of Drosophila melanogaster, "Texas". Out of a selection of 8 hexanucleotide specific restriction endonucleases, four restriction site and five DNA insertion/deletion variations were observed and the heterozygosity per nucleotide was 0.004. Linkage disequilibrium between two restriction sites, considerably removed from and on either side of the Adh transcriptional unit, identified two major classes of chromosome or haplotype in the population. These two haplotypes were strongly associated with the capacity of lines to respond to the environment (genotype-environment interaction) in ADH activity. It was concluded that a control or regulatory polymorphism was present in the population in association with the Adh transcriptional unit.