Molecular Evolutionary Genetics of Mexican Chromosomal Rearrangements in Drosophila pseudoobscura. Ian S. Leopold, Stephen W. Schaeffer. Department of Biology, The Pennsylvania State University, University Park, PA.

   Drosophila pseudoobscura has a wealth of chromosomal arrangements segregating on the third chromosome in the United States and Mexico. A recent sample of chromosomes collected from San Pablo Etla in Oaxaca, Mexico found the common Tree Line arrangement and a second common arrangement thought to be Cuenavaca based on cytological analysis. Cuernavaca is derived from the Santa Cruz arrangement by a single inversion step. Cytological analysis of these Cuernavaca and Santa Cruz chromosomes revealed a chromosomal looping pattern that was consistent with two rather than one inversion steps from Santa Cruz. DNA was extracted from two novel Cuernavaca strains and six Tree Line strains of Drosophila pseudoobscura. These DNAs were used to PCR amplify eighteen previously identified genetic markers for the third chromosome. These amplified samples were then purified and sequenced. Phylogenetic analysis was performed on the sequences using MEGA software. The phylogenies show that these Cuernavaca sequences are closely related to the Santa Cruz and Tree Line phylad. These data also served as quality control information for next generation sequence data collected by the Baylor College of Medicine.