Population Genetics of Drosophila Amylase
نویسنده
چکیده
Morph frequencies of three related polymorphisms were determined in ten natural populations of Drosophila pseudoobscura. They are the well-known inversion polymorphism of the third chromosome and the polymorphism for a-amylase produced by the structural gene A m y (which resides on the third chromosome). The third polymorphism was for tissue-specific expression of A m y in adult midguts; a total of 13 different patterns of activity have been observed. The preceding paper (POWELL and LICHTENFELS 1979) reports evidence that the variation in A m y expression is under polygenic control. Here we show that the polymorphism for midgut activity patterns occurs in natural populations and is not an artifact of laboratory rearing.-From population to population, A m y allele freuencies and frequencies of inversions belonging to different phylads vary coordinately. The geographic variation in &-amylase midgut activity patterns is uncorrelated with that for the other two types of polymorphisms. Furthermore, no correlation was detected between activity pattern(s) and A m y genotype(s) when both were assayed in the same individual.--These results imply that whatever the evolutionary-ecological forces are that control frequencies of the structural gene variants, they are not the same factors that control the frequencies of polymorphic genetic factors responsible for the tissue-specific expression of the enzyme. EVOLUTIONARY change requires genetic variation. We can recognize at least three basic kinds of genetic variation: variation in genes themselves (e.g., amino acid substitutions in proteins) , variation in the physical arrangement of genes (e.g. , inversions and translocations) and variation in control of gene expression. One of the most pressing problems facing evolutionary geneticists is to understand the comparative dynamics of these three types of genetic changes and their relative contributions to adaptive evolution. The a-amylase gene-enzyme system in Drosophila pseudoobscura offers a unique opportunity to study simultaneously all three types of genetic variation on the population level. Polymorphism for all three types of variation are known to affect amylase in this species. In D. pseudoobscura, a-amylase (E.C. 3.2.1.1, a-1, 4-glucan-4-glucanohydrolase) is coded for by a single gene ( A m y ) located at position 33 on chromosome ' Raeaich supported by National Science Foundation Grant DEB 76-19971. Genetic, 92: 613-622 June, 1979
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Population genetics of Drosophila amylase. IV. Selection in laboratory populations maintained on different carbohydrates.
Two polymorphic systems impinging on alpha-amylase in Drosophila pseudoobscura have been studied in laboratory populations maintained on medium in which the only carbohydrate source was starch (the substrate of amylase) and replicas maintained on medium in which the only carbohydrate source was maltose (the product of amylase). The two polymorphic systems were alleles at the structural gene (Am...
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