Genomes of organisms are subdivided into chromosomes. Comparisons among closely related species generally reveal differences in chromosomal organization as a result of rearrangements, yet chromosomal rearrangements in humans are associated with birth defects and cancers. The consequences of naturally occurring chromosomal rearrangements and the importance of genome reorganization are essentially unknown. Rearranged chromosomes within populations represent ideal systems for determining effects of chromosomal form on organismal function. A latitudinal cline for a chromosomal rearrangement in the fly Drosophila americana is an unusually tractable system for examining the significance of chromosomal form. This project will identify DNA sequence variation associated with alternative chromosomal forms, determine the influence of the rearrangements on the maintenance of this variation, and reveal differences among individuals owing to chromosomal form. These data will test the hypothesis that the alternative chromosomal arrangements in D. americana coordinate adaptive variation along this north-south climatic gradient.
Scientific training of students will be facilitated at multiple levels during the project. Two graduate students will be directly involved in data collection and analysis. Analyses of frequencies of the alternative chromosomal forms in natural populations of D. americana will be incorporated as an exercise in an undergraduate teaching laboratory. Students will gain unparalleled hands-on experience by performing and interpreting genetic analyses of genome organization.
