Mobile genetics sequences, or transposable elements, are ubiquitous features of mammalian genomes. They cause mutations by inactivation of genes, by changing the regulation of gene expressions, and by acting as sites for recombination which leads to chromosomal rearrangement. To understand the ways in which transposable elements affect the organisms, we need a more accurate assessment of transposition rates, and an understanding of the mechanisms by which elements within the genome interact. In this regard, it has been observed that elements compared from within a single species are generally more similar to each other than elements from two related species. This phenomenon, known as concerted evolution, suggests that elements are rapidly homogenized by some force(s) acting within a species. Concerted evolution is a common feature of transposable elements families, but is usually observed at the species level or above. This project examines a unique example of concerted evolution of transposable elements at the population level. Concerted evolution has been shown to occur in hundreds of copies of the mys retrotransposon in a single geographic population of the white- footed mouse, Peromyscus leucopus, near Orono, Maine. Although concerted evolution of mammalian transposable elements is generally believed to result from transposition by one or a few "molecular drivers", data from this population suggest that biased gene conversion may be the mechanism operating here. Furthermore, this gene conversion appears to effect only part of the mys element. The specific objectives of this project are: i) to determine the proportion of mys elements in the Maine population which have undergone concerted evolution; ii) to test the hypothesis that concerted evolution of mys within this population is due to biased gene conversion; and iii) to formulate hypotheses to explain the apparently limited region of the element undergoing gene conversion. Methods employed will include radioanalytic imaging of genomic Southern blots and DNA sequence comparisons of elements from the population of interest and orthologous elements from control populations. This study will be one of the first to examine the population biology of a mammalian transposable element. Concerted evolution in this population may well provide insight in to some previously unrecognized process by which transposable elements interact within the genome and influence the genetic basis of population adaptation to changing conditions.//
