INTERACTIONS BETWEEN THE AMYLASE AND ADIPOSE CHROMOSOMAL REGIONS OF DROSOPHILA MELANOGASTER.

Abstract

Estimation of the effects of substitution of one allele by another on the fitness of an organism is a primary goal of experimental population genetics. It is made difficult by the complex structure of genetic systems and by the dynamic complexity of selection in organisms with different developmental stages. The first problem is generally avoided by examining marginal fitness effects of a locus in a randomized genetic background. This is accomplished either by repeated intercrossing between strains differing in the two alleles of interest, or by sampling a large number of representatives of each allelic class from natural populations. The former method is of limited efficiency (Lewontin, 1974), and the latter, while it would yield a genetic background more representative of what is found in nature (Jones and Yamazaki, 1974) still does not allow one to make a firm causal connection between the locus being studied and fitness differences, due to the possibility of linkage disequilibria with background loci. An attempt was made to establish this causal link by demonstrating that genotypes of Drosophila melanogaster bearing high activity Amylase (Amy) alleles have a selective advantage over low activity variants when starch is the limiting carbohydrate source in the food medium (DeJong and Scharloo, 1976; Scharloo et al., 1977; Hoom and Scharloo, 1981). Hickey (1977, 1979) investigated the generality of this phenomenon by showing in a series of replicated population