Variation at the Cyp6g1 locus between two populations of Drosophila Melanogaster. Srna Vlaho, Matthew Salomon, Sergey Nuzhdin, Daniel Campo. MOLECULAR AND COMPUTATIONAL BIOL, UNIVERSITY OF SOUTHERN CALIFORNI, LOS ANGELES, CA.

   Understanding how different populations adapt to their local environment is fundamental to the study of how natural selection shapes the genetic makeup of different organisms by selecting for particular phenotypes. This study analyzes the variation in the Cyp6g1 gene between two populations of Drosophila melanogaster from Winters, CA and Raleigh, NC. This gene is of particular interest because it is known to confer resistance to the insecticide DDT. Previous work found that an increase in DDT resistance was associated with an increase in the copy number of the Cyp6g1 gene. In fact, a 330 kb region containing that gene was found to be highly divergent between the Raleigh and Winters populations of D. melanogaster. We genotyped a large number of individuals from both populations, and found that the BA and AA alleles, which contain two copies of the Cyp6g1 gene, were the most common alleles. Yet there were statistically significant differences between the allelic frequencies in Winters and Raleigh. The BA allele, which has been shown to confer a greater resistance to pesticides, was more common in the Winters population that was collected from an organic orchard, than in the Raleigh population that was sampled in a farmers market. It is possible that the most resistant allele was positively selected during many years, and now that the selecting agent DDT is not present anymore, the allele frequencies are coming back to equilibrium. In addition, we discovered a new genotype in one of the Raleigh lines that could give it an enhanced resistance to pesticides. We are currently performing functional experiments with our populations to determine a relationship between the genotypes we observed and the level of resistance to pesticides.