Genomic parasites -- One of the major finding of this new era of genomic research is how ubiquitous and tremendously important repetitive DNA elements (i.e. transposable elements) have been in shaping eukaryotic genetics. There are implications for the origin of DNA-based inheritance, sex, chromatin structure, and total genome size. Despite their clear implications to the biology of several model systems, we have not yet investigated repetitive DNA elements in a sufficiently broad sampling of organisms to draw steadfast rules about their biology. Microbotryum has provided an excellent example of a system that contradicts several emerging assumptions. In comparison with previously examined fungi with similarly sized genomes, Microbotryum has many times the density of repetitive DNA elements. It also contains of a broad range of repetitive DNA types (Copia, Gypsy, Non-LTR, and Helitron-like elements), which is in contrast to the idea that highly selfing lineages should be poor in repetitive element diversity. Current research is directed toward understanding the origins and maintenance of these elements in Microbotryum, and in particular, how their numerical dynamics are influenced by the presence of dimorphic sex chromosomes.