ENVIRONMENT-INFLUENCED EXPRESSION OF POLYGENE MUTATIONS ISOLATED FROMA NATURAL-POPULATION OF DROSOPHILA-MELANOGASTER

Quantitative trait loci (QTLs) affecting sternopleural bristle number in Drosophila melanogaster have been mapped using phenotypic markers a nd progeny testing. The loci were found on four of the third chromosom es isolated from a natural population. All four loci showed large effe cts at the standard 25 degrees C culture temperature, but they respond ed in different ways when developmental temperature was lowered or rai sed. These data support the hypothesis that genotype x environment int eractions have important influences on polygene expression, and some l oci might be silent, or phenotypically neutral, under some conditions but play a large phenotypic role under others. Thus, a full cataloging of the loci contributing to mutational variance for QTLs cannot be do ne at just a single, controlled environmental condition.