| Gene duplications and chromosomal rearrangements differentiate multiple genomes taken from a single species and genomes from different species. The mechanisms by which genes are duplicated and the content of a genome is rearranged are of interest in both the biomedical and biological communities. Additionally, the evolutionary dynamics of these structural variations have become a topic of great interest in the post-genomic era. The research presented in this thesis examines the origin and evolution of duplicated genes and chromosomal rearrangements using the model organisms of the Drosophila genus. The effects of chromosomal inversions on meiosis were examined in D. pseudoobscura, and it was found that they do not affect the segregation of homologs. Recently duplicated genes were identified in the D. pseudoobscura genome. The mechanisms responsible for the duplications were determined, as was the amount of selective constraint on different classes of genes. Duplicated genes were also used to study the evolutionary dynamics of sex chromosomes. Positive selection appears to be more effective on X-linked, as opposed to autosomal, derived copies of duplicated genes. Additionally, duplicated genes tend to move off the X chromosomes of most Drosophila species. The forces responsible for this pattern depend on the species in question as well as the sex-bias of the gene that is duplicated. Finally, genes that are duplicated off of new X chromosomes are under less selective constraint than those duplicated off of other chromosome arms. These results indicate that the evolutionary dynamics of duplicated genes depend on a wide variety of factors, including: the mechanism by which a gene is duplicated, the chromosomal context into which it is duplicated, and the type of gene that is duplicated. No single predictor determines whether a duplicated gene is selectively preserved, however multiple properties of a duplicated gene influence its evolutionary trajectory. |
