High resolution electrophoretic variation at the esterase-6 locus in a natural population of Drosophila melanogaster

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Abstract
One hundred and fifty-seven lines isoallelic for esterase-6 were extracted from a natural population of D. melanogaster. The relative electrophoretic mobilities of Est6 allozymes in the different lines were determined by repeated pair-wise comparisons on high resolution cellulose acetate plates. Ten allozymic classes were resolved among the lines where only four, Est6-VF, Est6-F' Est6-F and Est6-S, had been evident using standard electrophoretic procedures. The additional variation resulted from the subdivision of Est6-F and Est6-S into three and five classes respectively. Genetic analyses confirmed that the additional classes mapped at or near the Est6 locus. Two of the additional classes occurring at low population frequencies were associated with significantly higher third chromosome viabilities. The most frequent class within Est6-F was in significant gametic disequilibrium with the linked polymorphic inversion In(3L)P. The same high resolution procedures were applied to 13 lines of D.melanogaster representing six Est6 thermostability variants. Different thermostability variants did not group consistently according to electrophoretic classes. This implies that the two criteria are detecting protein variation independently from each other and that much greater variation occurs than is detected by either criterion alone.